合同
合同概述Overview of Contracts
合同的适用法律Applicable Law of Contracts
Contracts for the sale of goods are governed by Article 2 of the Uniform Commercial Code ("UCC"), leases of goods are governed by UCC Article 2A (Note: UCC Article 2A is generally not tested on the MBE and is for your information only), and other contracts are governed by the common law. The definition of "goods" is all things movable. Therefore, real estate is not considered "goods".
物品买卖合同适用《统一商法典》第2条（Article 2 of the Uniform Commercial Code, “UCC”），物品租赁适用UCC第2A条（注意：UCC第2A条通常不是MBE的考察重点，只需了解即可），其他合同适用普通法。对“物品”的定义是可移动的（all things movable）。所以房地产不是“物品”。
Both the sale and development of real estate are governed by the common law. Sometimes you may see a question where a seller sells houses in a package; do not mistakenly assume that the UCC applies.
无论是房地产的买卖还是开发，都适用普通法。有时候看到题目中卖家把房子打包卖，不要误以为适用UCC.
A sells a used car to B for a price of $0. This is not a sale, but a gift. The gift of goods is also generally governed by the common law.
甲卖给乙一辆二手车，价格为0. 这不是买卖，而是赠与，物品的赠与也一般适用普通法。
The common law system, also known as the case law system, originated in England and is primarily based on judicial precedents. For these types of rules, I cannot tell you what the statutory basis is, because they are general rules gradually established through a large number of ancient precedents by English judges. Fortunately, the legal community has summarized the application of the common law in the United States through the Restatements of the Law, so I may find some provisions from the Restatement to support a certain common law viewpoint.
普通法系又叫判例法系，来源于英国，以判例为主。对于这类规则，我没有办法回答你法律依据是什么，因为是通过大量英国法官的古早判例慢慢确立起来的一般规则。好在法学界通过法律重述（Restatement）将普通法在美国的适用进行总结，所以我可能会从法律重述中找到一些条文来支持某普通法观点。
In contrast, there is the civil law system, also known as statutory law. The United States is a common law country, but statutory law is also widely applied. For example, the U.S. Constitution is written law, and the UCC is also a statutory code.
与此相对的是大陆法系，也叫成文法。美国是普通法国家，但成文法也大量适用，比如美国宪法就是成文法律，UCC也是一部成文法典。
When determining whether to apply the common law (case law) or statutory law, the following rules are generally adopted:
适用普通法（判例）还是成文法时通常采取如下规则：
Torts, Criminal Law, and Real Property are subjects primarily based on the common law. Evidence is a purely statutory subject (though contents related to privileges are common law). Although Constitutional Law and Criminal Procedure involve studying the text of the Constitution, their content consists of the Supreme Court's interpretations of the Constitution. Civil Procedure seems to test federal rules, but it has strong common law and constitutional undertones. Contracts is a classic subject where more than half is common law, a smaller portion is the UCC (statutory law), and a little bit is equity. Although it is a mixture, it is simple and very suitable for beginners.
侵权、刑法、房地产是以普通法为主的科目。证据法是纯法条的科目（其中和特权有关的内容是普通法）。宪法、刑诉虽然是学宪法原文，但其内容是最高法院对宪法的解释。民诉看似考的是联邦法条，但普通法和宪法色彩浓厚。合同则是经典的一大半学普通法，一小半学UCC（法条），还有一点点学习衡平法，虽然杂糅，但是简单，非常适合入门。
When a contract involves both services and the sale of goods, we use the predominant purpose of the contract to determine the applicable law. However, if the contract can be divided into goods and non-goods portions, the court may separate them.
当一个合同同时有服务和商品买卖时，我们用合同的主要目的考虑法律适用。但是如果合同可以被分割为实物部分和非实物部分，法院有可能会把他们分开。
Contracts for building a house, renting a house, or selling a house: Common law.
盖房、租房合同、房屋买卖合同：普通法
Car rental: UCC Article 2A.
租车：UCC Article 2A
Sale of an air conditioner with on-site installation services: UCC Article 2.
出售空调和上门安装的服务：UCC Article 2
Attorney Yuan tutors for the US Bar Exam while selling a textbook and charging a package fee: Common law.
袁律师辅导美国司考的同时销售了一本教材并打包收费：普通法
Attorney Yuan charges $1,000 for US Bar Exam tutoring and sells a textbook for $50: Handled separately.
袁律师辅导美国司考收费1000美金，并以50美金出售教材：分开处理
Patents: Common law.
专利：普通法
Microsoft Windows CD-ROM: UCC Article 2.
Microsoft Windows光盘：UCC Article 2
合同的形成Formation of Contracts
合意Mutual Assent
The formation of a contract requires mutual assent, meaning the offeror makes an offer and the offeree accepts the offer.
合同的形成需要双方达成合意（mutual assent），即提出方（offeror）提出要约（offer），被提出方（offeree）接受要约（acceptance）。
要约Offer
有效要约Valid Offer
To analyze whether an offer is valid, consider the following three elements:
分析一个要约是否有效，考察以下三个要素：
A says: 'I am considering whether to sell my car to you for $5,000.' A has no present intent to be bound, so this is not an offer.
甲说：我在考虑是不是要把我的车以5000元卖给你。甲没有履约的意思表示，不是要约。
A writes an offer, leaves it in a drawer, and later accidentally mails it along with other letters. This is a valid offer. We look at whether the other party could reasonably believe the offeror intends to be bound, rather than the offeror's subjective state of mind.
甲把要约写好后放在抽屉里，后来不小心和其他信件一起寄走了。这是一个有效的要约，我们看的是对方是否能合理认为提出方有履约的意思表示，而不是看提出方的主观心态。
Contracts for the sale of goods do not require a stated price. Cook writes to Gates: "Please buy a pair of AirPods Max." Gates replies: "OK." A contract is formed, and the price of the headphones is supplied by UCC gap-filling rules, which would likely be the retail price on Apple's official website.
物品买卖不需要注明价格。库克给盖茨写信：请买一副AirPods Max. 盖茨回复：好的。合同成立，耳机价格用UCC的规则补足，大概率就是苹果官网的售价。
A contract for the sale of goods may not even need a highly specific description of the subject matter. It can be understood that the parties have reached a tacit understanding regarding the subject matter; for example, for a buyer and seller who only trade in crude oil, specifying the quantity is sufficient.
物品买卖合同甚至不需要具体的标的物。可以理解为双方对标的物已经达成了某种默契，比如对于只交易原油的买家和卖家，约定数量就已经足够。
A writes on a napkin: 'I offer to sell my house in San Jose to B for $2 million.' A owns only one house in San Jose. This is a valid offer. If B accepts, the real estate transaction can be completed in a reasonable manner and within a reasonable time. However, if A owns multiple houses in San Jose, the real estate contract would fail to form because the subject matter cannot be identified.
甲在餐巾纸上写到：我提出把圣荷西的房子200万元卖给乙，甲在圣荷西只有一套房。这是一个有效的要约。如果乙接受，房屋以合理的方式、在合理的（reasonable）时间内交易完毕即可。但如果甲在圣荷西有多套房子，则房地产买卖合同因无法确定标的物而无法成立。
A posts a reward advertisement: 'Anyone who finds my dog will be rewarded $200.' B does not see the ad but finds the dog and returns it to A. Because B is unaware of A's reward offer, no contract is formed.
甲发布悬赏广告：任何人找到我的狗将奖励200元。乙没有看到广告，但找到了狗并还给了甲。乙不知道甲的悬赏广告，合同不成立。
悬赏广告Reward Advertisements
Reward advertisements are considered offers. In the above example, if B had seen the ad and found the dog, it would be deemed an acceptance of the offer.
悬赏广告视为要约。在上例中，倘若乙看到广告并找到了狗，视为接受要约。
传单Flyers / Advertisements
General advertisements or flyers are not offers, but advertisements that limit the quantity and are on a first-come, first-served basis are considered offers.
一般的传单不是要约，但有限定数量、先到先得的传单视为要约。
A seller writes on a flyer: 'Cabbage for $0.50 per pound.' This is not an offer. If a buyer sees the flyer and faxes the seller to purchase 10 pounds of cabbage, the buyer is making an offer, not accepting one.
卖家在传单上写：白菜5毛钱一斤，不是要约。买家看到传单后传真甲采购10斤白菜则是提出要约，而不是接受要约。
A seller writes on a flyer: 'On August 1, cabbage is $0.50 per pound, while supplies last.' This is considered an offer. If a buyer goes to the seller on August 1, sees the cabbage, and selects 10 pounds, this is deemed an acceptance, and the seller must sell it at $0.50 per pound.
卖家在传单上写：8月1日的白菜5毛钱一斤，售完为止，视为要约。买家8月1日前往卖家处看到白菜并选购10斤，视为接受要约，卖家应当按照5毛钱一斤销售。
A seller writes on a fax: 'Selling 10 pounds of cabbage,' and faxes it to a buyer. This is an offer. The buyer purchasing the 10 pounds of cabbage after seeing the fax is an acceptance.
卖家在传真上写：出售10斤白菜，并传真给买家，这是要约。买家看到传真后采购10斤白菜则是接受要约。
要约的终止和撤回Termination and Revocation of Offers
要约失效Termination of Offers
A general offer terminates once it is rejected, and it is of no use even if the rejecting party changes their mind. Bargaining is considered a rejection accompanied by a new offer, known as a counteroffer, but a mere inquiry as to whether there is room for a price reduction does not fall under this rule.
一般的要约被拒绝后失效，即使拒绝人反悔也无济于事。讨价还价视为拒绝的同时提出新的要约，或者叫反要约（counteroffer），但单纯询问是否有降价空间不在此例。
Seller says: 'I will sell you this watch for $400.' Buyer says: 'I will only consider buying it for $300.' At this point, the buyer is deemed to have rejected the offer and made a counteroffer of $300. The seller's offer terminates. A day later, the buyer replies: 'I am willing to buy it for $400.' This is not considered an acceptance, but rather a new offer to buy for $400.
卖家说：这款手表400元卖给你。买家说：我只考虑300元买。此时买家视为拒绝了要约并提出了300元的要约。卖家的要约失效。一天后买家回复说：我愿意400元购买，不视为接受要约，而视为提出了新的400元的要约。
Seller says: 'I will sell you this watch for $400.' Buyer says: 'Could you sell it to me for $300?' Seller says: 'That is already the lowest price.' Buyer says: 'Then $400 it is.' The buyer is deemed to have accepted the seller's offer.
卖家说：这款手表400元卖给你。买家说：能不能300卖给我？卖家说：已经最便宜了。买家说：那就400吧。买家视为接受了卖家的要约。
An offer terminates if it is not accepted within a reasonable time (seasonably).
没有在合理的时间内（seasonable）接受要约，要约失效。
A cabbage stand is about to close, and the vendor tells an elderly lady the price is $0.20 per pound. The next morning, while the cabbage is still fresh, the lady agrees to the vendor's quote. The lady did not accept the offer in a timely manner, so no contract is formed.
白菜摊要收摊了，摊主对大妈说2毛钱一斤，大妈第二天早上趁白菜新鲜时同意摊主的报价。大妈没有及时接受要约，合同不成立。
An offer terminates if either party dies or becomes mentally incapacitated before the contract is formed. Note that a contract does not automatically terminate due to the death of a party after the contract is formed.
合同成立之前任何一方死亡或者陷入无民事行为能力，要约失效。请注意，合同成立后并不会当然因为一方的死亡而失效。
A seller mails an offer to sell a house to a buyer. After the buyer receives it, the seller dies. The buyer, unaware of the death, still mails an acceptance. No contract is formed. The offer terminated at the time of the seller's death.
卖家将卖房的要约寄给买家，买家收到后卖家死亡。买家在不知情的情况下依然寄出了acceptance，合同没有成立。在卖家死亡时，要约已经失效。
However, if the buyer dies after a real estate contract is formed, the funds can be executed from their estate; if the seller dies, it does not affect the continued transfer of the property, so the contract remains valid. In contrast, if either party dies after a tutoring contract is formed, it renders the contract impossible to perform or meaningless to perform. We will learn about situations where contracts are discharged later in the text.
但如果房屋买卖合同已经成立后买方死亡，可以执行他遗产中的钱款；卖方死亡，也不影响房屋继续过户，所以合同依然有效。作为对比，家教合同成立后，任何一方死亡，会导致合同不可履行、履行不再有意义，我们会在后文学到合同解除的情形。
撤回Revocation
The offeror may revoke the offer at any time before acceptance. Once the offeree learns that the offer has been revoked, any subsequent acceptance is invalid. Revocation can be expressed explicitly, or it can be communicated through other means that lead the offeree to believe the offer has been revoked, such as selling the house to a third party, and the offeree learns of this from a reliable third party.
提出要约的人可以在接受之前任意撤回要约，对方一旦知悉要约被撤回后再接受是无效的。撤回可以明确表示，也可以通过其他方式让被提出人相信要约已经撤回，比如将房屋卖给第三人，且被提出人从可靠的第三方处知晓此事。
If the offeree accepts the offer before learning of the revocation, the contract is already formed, and the revocation fails.
如果被提出要约的人知悉撤回要约之前同意了要约，则合同已经成立，撤回失败。
不可撤回的要约Irrevocable Offers
Under common law, an irrevocable offer is treated as a separate option contract, which is no different from other contracts. Since it is a contract, it requires the offeree to pay some consideration to keep the option open for a period of time. This promise does not need to be in writing.
普通法中，不可撤回的要约视为一个单独的选择权合同（option contract），它和其他的合同没什么区别。既然是合同，就要求对方支付一定的对价（consideration），用于将选择权保留一段时间。该承诺不需要书面作出。
A says: 'I will lease Blackacre to you for $1,000 a month.' B says: 'Please let me think about it for a month.' A agrees. However, because B paid no consideration, an irrevocable offer was not formed. On the third day, A notifies B that Blackacre has already been leased to C for $2,000 a month, which constitutes a valid revocation of the offer. Note, however, that if B had accepted the offer on the second day, or if B accepted on the fourth day without having learned that A had leased it to C, B could still validly accept the offer, and a contract would be formed. As for the simultaneous formation of two lease contracts, this is handled under breach of contract theories.
甲说：我把黑土地租给你，每个月1000元。乙说：请让我考虑一个月。甲同意。但因为乙没有支付对价，并没有成立不可撤回的要约。第三天甲通知乙已经将黑土地以2000元一个月租给了丙，视为有效撤回要约。 但注意，如果乙在第二天就同意了要约，或者乙虽然是第四天同意的要约，但他并未得知甲已经租给了丙，依然可以有效接受要约，合同成立。至于同时成立了两个租赁合同，用违约理论处理。
A says: 'I will lease Blackacre to you for $1,000 a month.' B says: 'I will give you $100 to let me think about it for a month.' A agrees. The next day, A notifies B that Blackacre has been leased to C for $2,000 a month. A has breached the option contract. If B intends to lease Blackacre within that month, B can claim damages.
甲说：我把黑土地租给你，每个月1000元。乙说：我给你100元，请让我考虑一个月。甲同意。第二天甲通知乙已经将黑土地以2000元一个月租给了丙。甲违反了option contract，乙如果在一个月内打算租赁黑土地，可以主张损害赔偿。
An option contract remains valid until it expires even if it is initially rejected (the offeree can change their mind), unless the offeror materially relies on the rejection.
Option contract被拒绝后，到期之前依然有效（可以反悔），除非提出人基于对拒绝的信赖作出了后续行为。
A writes to O: 'I intend to buy Blackacre and am willing to pay $3,000 in exchange for you keeping the offer to sell Blackacre for $300,000 open to me for 30 days.' O replies: 'OK.' The next day, A writes to O: 'I no longer need Blackacre.' On the third day, A writes to O: 'I am willing to buy Blackacre for $300,000.' A real estate contract is formed.
A给O写信：打算购买黑土地，愿意支付3000美元，换取把黑土地以30万的价格保留给我30天。O回信：好的。第二天，A给O写信：已经不需要黑土地。第三天，A给O写信：愿意以30万价格购买黑土地。房地产买卖合同成立。
A writes to O: 'I intend to buy Blackacre and am willing to pay $3,000 in exchange for you keeping the offer to sell Blackacre for $300,000 open to me for 30 days.' O replies: 'OK.' The next day, A writes to O: 'I no longer need Blackacre.' On the third day, O sells the land to B. The option contract is no longer effective.
A给O写信：打算购买黑土地，愿意支付3000美元，换取把黑土地以30万的价格保留给我30天。O回信：好的。第二天，A给O写信：已经不需要黑土地。第三天，O把土地卖给了B. Option Contract不再有效力。
The UCC does not explicitly provide for option contracts, but keeping an option open with consideration is consistent with the freedom of contract in the sale of goods and is valid. Alternatively, since an option to buy goods is not itself a contract for the sale of goods, it can be considered governed by common law.
UCC没有明确规定option contract，但对价保留option的方式也符合货物买卖合同的意思自治，是有效的。或者，保留货物买卖选择权本身不是货物买卖合同，也可以认为它本就归普通法管辖。
In addition, the UCC allows another way to make an offer irrevocable, called a firm offer, which requires:
除此之外，UCC还允许用另一种方式保留offer不可撤销，叫做firm offer，要求：
The UCC defines a merchant as 1. a person who deals in goods of the kind, or 2. a person who has specialized knowledge or skill regarding the practices or goods involved. A student pointed out that if Microsoft purchases Apple phones, Microsoft is not a merchant. This makes sense under the first definition, as Microsoft no longer trades in phones. The following assumes Microsoft is an entity with specialized knowledge in purchasing phones, while Gates is not; therefore, 'Microsoft' below is a merchant, but 'Gates' is not. 'Apple' and 'Cook' are both merchants selling phones: individuals can also be merchants. In the MBE, the parties in UCC questions are typically merchants.
UCC对商家的定义是指1. 专门买卖某种货物的人，或者 2. 对买卖某种货物有特殊知识或技能的人。有学员指出，微软采购苹果的手机，微软并不是商家，这在第一种定义的商家中是有道理的，因为微软已经不再交易手机了。下文假设微软是具有购买手机专门知识的人，而盖茨没有，所以下文中的“微软”是商家，但“盖茨”不是。“苹果”和“库克”则都是卖手机的商家：个人也可以是商家。在MBE中，考UCC的题目中出现的角色通常都是商家。
Cook writes to Gates: 'If you buy an Apple phone, you can buy one for $500, valid for one year.' This is a firm offer, which must be held open for the shorter of three months or the time stated in the offer. Two months later, Cook changes his mind. However, within three months, Gates can still buy an Apple phone for $500.
库克给盖茨写信：如果你买苹果手机，可以500美金买一台，一年内有效。这是firm offer，最短要保留三个月或offer中注明的时间中的较短者。2个月之后，库克反悔。但3个月之内，盖茨都可以以500美金买一台苹果手机。
Cook writes to Gates: 'If you buy an Apple phone, you can buy one for $500, valid for one year.' Nine months later, Cook changes his mind. After the revocation, the offer is no longer valid. However, if Cook had not revoked it, the offer would still be valid.
库克给盖茨写信：如果你买苹果手机，可以500美金买一台，一年内有效。9个月之后，库克反悔。反悔后要约不再有效。但库克没有反悔时要约依然有效。
Cook writes to Gates: "If you buy an iPhone, you can have one for $500." Gates replies: "I am willing to pay $100 to keep your offer open for 1 year." Cook agrees. Although the sale of goods is governed by the UCC, an option contract supported by consideration is governed by general contract law principles, and therefore is not subject to the three-month limit of the UCC Firm Offer rule. Four months later, Cook reneges. However, within the one-year period, Gates can still buy an iPhone for $500.
库克给盖茨写信：如果你买苹果手机，可以500美金买一台。盖茨回复：我愿意支付100美金让你的要约1年内有效。库克同意。虽然货物买卖适用UCC，但有对价支持的期权合同适用一般合同法原则，因此不受UCC Firm Offer三个月期限的限制。4个月之后，库克反悔。但一年之内，盖茨都可以以500美金买一台苹果手机。
Cook writes to Gates: "I am willing to sell you my prized antique car for $500, valid for three months." One month later, Cook reneges. Since Cook is not a merchant of antique cars, the offer is no longer valid.
库克给盖茨写信：我愿意500美金卖给你我珍藏的那台古董车，三个月内有效。一个月后库克反悔。库克不是卖古董车的商家，要约不再有效。
接受要约Acceptance of an Offer
谁能接受Who Can Accept
Generally, only the person to whom the offer is made can accept it.
通常只有被提出要约的人能接受要约。
A says to B: "Marry me." C overhears and says: "I do." Even if A's statement is an offer, no contract is formed.
甲对乙说：嫁给我。丙听到后说：我愿意。即使甲提出的是要约，合同也没有成立。
However, an option contract is generally assignable because the option itself is considered a contract supported by consideration.
但option contract通常可以转让，因为option本身就应当视为一个有对价的合同。
通过行为接受要约Acceptance by Performance
A unilateral contract must be accepted by completing a specific task; thus, the offer is accepted only when the task is completed. Merely beginning the task only makes the offer irrevocable.
单方合同（unilateral contract）必须通过完成特定的任务来接受，那么任务完成才算是接受要约，仅仅开始任务只是让这个要约变得无法撤回。
A says: "I will reward $1,000 to anyone who finds my dog." B searches for the dog for 3 days, at which point A revokes the offer. B continues searching and finds the dog on the 5th day. A contract is formed, and A must pay $1,000. Once B begins searching for the dog, the offer becomes irrevocable.
甲说：谁找到我的狗就奖励1000元。乙找了3天狗，甲撤回要约，乙继续找狗，第5天找到了狗，合同成立，甲需要支付1000元。乙一旦开始找狗，要约就无法撤回。
A says: "I will reward $1,000 to anyone who finds my dog." B begins searching for the dog with great fanfare. Because B is a dog-finding expert, everyone else gives up searching. B gives up searching after three days. B has not accepted the contract, and A cannot claim damages from B.
甲说：谁找到我的狗就奖励1000元。乙大张旗鼓开始找狗，因为乙是找狗专家，其他人都放弃找狗，乙三天后放弃找狗。乙没有接受合同，甲无法向乙主张损失。
The vast majority of contracts are bilateral contracts. They can be accepted by a promise, but beginning performance is also considered acceptance.
绝大部分合同都是双方合同（bilateral contract）。通过承诺可以接受合同，但直接开始履行同样视为接受合同。
A says to B: "I will pay you $1,000 to paint my room." B agrees, and a contract is formed.
甲对乙说：支付你1000元把我的房间粉刷一遍。乙同意，合同成立。
A says to B: "I will pay you $1,000 to paint my room." B says nothing but directly starts painting the wall. A contract is formed.
甲对乙说：支付你1000元把我的房间粉刷一遍。乙没有说话，而是直接开始刷墙，合同成立。
We must remember that a unilateral contract is defined as one that can only be accepted by complete performance. If the offer explicitly states that the offeree must accept by completing a task, it is, of course, a unilateral contract.
我们谨记单方合同的定义是只能通过完美履行来接受合同，如果要约明确点出需要对方通过完成任务接受要约，那当然是单方合同。
More often, however, it is not easy to tell from the offer itself whether it invites acceptance by a promise or by complete performance. Distinguishing between a unilateral and a bilateral contract in such cases requires technical analysis. We need to consider simultaneously:
但更多的时候，要约本身不容易看出是在邀请对方通过言语还是完美履行来接受合同，这时如何区分单方还是双方合同是个技术活。我们需要同时考察
A has 10,000 parts and offers to pay B only if B finds a buyer willing to purchase them for more than $1 each. B verbally agrees. First, this is a service contract, so the common law applies rather than the UCC. Second, this is a unilateral contract. Although, unlike the dog-finding example above, it is made to only one person, it does not seem exclusive (multiple people could be asked to find a buyer simultaneously). If B gives up looking for a buyer, it would seem unfair to consider B in breach. Therefore, B's verbal "agreement" has no legal effect; only actually finding a buyer constitutes acceptance of the offer. B's act of beginning the search for a buyer can only be viewed as making the offer irrevocable, rather than forming a service contract to find a buyer.
甲有10000个零件，向乙提出只有找到以1美元以上的价格购买这批零件的买家才支付报酬，乙口头同意。首先，这是服务合同，适用普通法而不是UCC。其次，这是单方合同。虽然它和上述找狗不同，它只针对一个人提出，但似乎并不排他（可以同时让多人找买家）。如果乙放弃寻找买家，将乙视为违约似乎并不公平。因此，乙口头上的“同意”没有法律效力，只有实际找到买家才算接受要约。乙开始寻找买家的行为只能视为要约不可撤回，而不是成立了一个找买家的服务合同。
A mails an artifact to B for restoration. After beginning the restoration, B finds it too difficult and gives up. This is a bilateral contract; B's act of beginning the restoration is considered acceptance of the contract, and giving up is considered a breach. This is because: 1. the offer is made to a single person; 2. restoring the artifact is exclusive; and 3. it is difficult to hand it over to someone else halfway through the restoration, making it fairer to treat the abandonment as a breach.
甲将文物邮寄给乙修复，乙开始修复后发现修复难度过大，于是放弃。这是双方合同，乙开始修复的行为视为接受了合同，放弃修复视为违约。因为1、要约是针对一个人提出，2、修复文物是排他的，3、修复到一半再交给其他人修复是有难度的，视为违约更加公平。
When it is difficult to distinguish, the majority view is that contracts are presumed to be bilateral by default. An offer creates a unilateral contract only if it explicitly requires complete performance for acceptance.
在不好区分的时候，多数说认为合同默认都是双方的，除非offer明确要求用履行完毕来接受合同，才是单方的。
普通法：镜子规则Common Law: The Mirror Image Rule
Under the common law, an acceptance must exactly match the offer to be valid. Adding any conditions will be treated as a counteroffer, unless the condition is already implied in the offer. This is known as the mirror image rule.
在普通法下，要约的接受必须和提出一模一样才有效，附加任何条件都会被视为反要约（counteroffer），除非这个条件本来就隐含在要约中。这也被称作镜子规则（mirror rule）。
A asks: "Please come clean my house, I will pay $300." The cleaning company replies: "You must pay in cash to get this price." The cleaning company normally accepts cash, credit cards, and checks. No contract is formed; the condition requiring cash payment is treated as a counteroffer.
甲问：请来打扫我家，支付300元。清洁公司说：必须支付现金才能给到这个价格。清洁公司本来接受现金、信用卡和支票。合同没有成立，要求付现金的条件视为反要约。
The cleaning company says: "$300 for one cleaning." A says: "I am willing to pay $300 in cash." The cleaning company normally only accepts cash, so cash payment is considered implied in the offer. A contract is formed.
清洁公司说：300元打扫一次。甲说：我愿意支付300元现金。清洁公司本来就只接受现金，现金支付视为隐含在要约中，合同成立。
The cleaning company says: "$300 for one cleaning." A says: "That is absolute robbery, but I am too lazy to find another company." A contract is formed. Grumbling about or commenting on an offer does not constitute a rejection.
清洁公司说：300元打扫一次。甲说：简直是在抢钱，但是我懒得去找别家了。合同成立。对要约的评价不构成拒绝要约。
邮箱规则The Mailbox Rule
In China, regular mail has largely disappeared. Offers and acceptances are usually made via phone, email, WeChat, or other instant messaging methods, or at least by express delivery that arrives in 1-3 days. However, regular mail is still widely used in the United States, and making and accepting offers is no exception.
在中国，平信基本已经销声匿迹。提出和接受要约通常都是用电话、电子邮件、微信等即时通讯的方式，最次也是1-3天就能送达的快递。但平信在美国依然被大量使用，提出和接受要约也不例外。
Unless explicitly agreed otherwise, an acceptance is effective upon dispatch. This is known as the mailbox rule.
除非有明确约定，接受要约以寄出时生效，这叫做邮箱规则（mailbox rule）。
A writes a letter offering to sell his luxury watch to B for $5,000. Upon receiving it, B mails back, "I accept your offer." The contract is formed when the letter is dispatched.
甲写信邀请乙5000美元购买他的一块名表，乙收到后寄出“同意你的要约”。合同在平信寄出时成立。
A writes a letter offering to sell his luxury watch to B for $5,000, but B is unaware of it. Coincidentally, B simultaneously writes a letter to A offering to buy A's watch for $5,000. Although their offers are strikingly identical, they are merely two crossing offers, and no contract is formed.
甲写信邀请乙5000美元购买他的一块名表，但乙并不知情。巧的是，乙同时写信寄给甲邀请5000美元购买甲的这块手表。虽然两个人的要约惊人地一致，但也仅仅是两个要约而已，并没有成立合同。
Unless specifically distinguished in this handout, the rules under the common law and the UCC are similar.
在本讲义没有特意区分的时候，普通法和UCC的规定是类似的。
Conversely, a rejection or revocation of an offer is effective upon receipt. For example, if an acceptance is dispatched first and a rejection is dispatched later, a contract is already formed when the acceptance is dispatched. The exception is if the offeror receives the rejection letter first and detrimentally relies on it by making subsequent arrangements.
而拒绝、撤回要约则是对方收到时生效。比如先寄出同意要约，后寄出拒绝要约，则前一个寄出时合同已经成立。除非提出要约的人先收到了拒绝要约的信，并基于对拒绝的信赖作出后续安排。
If a rejection is dispatched first, followed by an acceptance, the mailbox rule does not apply; whichever letter the offeror receives first controls.
如果是先寄出拒绝要约，后寄出接受要约，以对方先收到的信为准，不适用邮箱规则。
Similarly, if the offeror revokes the offer, but the offeree dispatches an acceptance before learning of the revocation, the contract is still formed. However, if the offeree is already aware that the offer has been revoked, they cannot accept it.
同理，如果要约提出人撤回要约，对方知悉被撤回之前寄出了同意要约，则合同依然成立。但如果已经知悉要约被撤回，被提出人无法同意要约。
Although these rules are slightly difficult to memorize, you will become familiar with them and eventually remember them through practice questions. If you really cannot remember, keep one principle in mind: as in China, the underlying policy is to facilitate transactions and favor the formation of contracts.
这些规则虽然稍微有点难记，但你会在做题中熟悉并最终记住。如果实在记不住，可以记一个原则：和中国一样，以促进交易、倾向合同成立为原则。
普通法：默示接受Common Law: Acceptance by Silence
The common law generally requires the offeree to expressly accept an offer through verbal communication. However, if under specific circumstances a reasonable person's silence indicates acceptance, courts will usually find that a contract is formed, especially when the silent party receives a benefit. In such situations, the offeree has a duty to notify the offeror of an explicit rejection; otherwise, a contract is deemed formed.
普通法通常要求接受的人通过语言的沟通明示接受要约。但是如果在特定情境下，一个理性的人的沉默表示接受了要约，法院通常会判合同成立，尤其是沉默方获得利益时。在这种情形下，被提出要约的人有义务通知提出人他明确拒绝要约，否则视为合同成立。
A offers to clean B's yard for $50. B is noncommittal but stands by and watches A finish cleaning the yard. A reasonable person would explicitly object if they did not accept the offer. A contract is formed.
甲提出给乙打扫院子并收取50元，乙不置可否，但眼睁睁看着甲把院子打扫完毕。一个理性的人如果不接受要约会提出明确反对。合同成立。
UCC：格式冲突UCC: Battle of the Forms
The UCC does not require the terms of the acceptance to exactly match those of the offer. If the offeree proposes new terms or even modifies some of the offeror's terms, it can still be considered an acceptance. This situation is referred to as the "battle of the forms."
UCC并不要求要约的提出和接受方的条件一模一样，如果接收方提出了一些新的条件，甚至修改了一些提出方的条件，依然可以视为接受要约。这时我们称双方的制式表格有冲突（battle of forms）。
Whether the new or modified terms proposed by the offeree become part of the contract depends on the circumstances.
接受方提出或修改的条件要视情况决定是否能成为合同的一部分。
Cook writes to Gates: "If you buy AirPods Max, it's only $500 a pair." Gates replies: "I am willing to buy a pair for $500 with free shipping." A contract is formed, but since Gates is not a merchant, the free shipping term is treated as a proposal rather than part of the contract.
库克给盖茨写信：如果你买AirPods Max，只需要500美金一副。盖茨回复：我愿意500美金包邮买一副。合同成立，但盖茨不是商家，包邮条款视为提议而不是合同的一部分。
Apple writes to Microsoft: "If your company buys AirPods Max, it's only $500 a pair." Microsoft replies: "We are willing to buy a pair for $500 with free shipping." For headphones, shipping costs do not constitute a material alteration. A contract is formed, and it includes the free shipping term.
苹果给微软写信：如果贵司买AirPods Max，只需要500美金一副。微软回复：愿意500美金包邮买一副。对耳机来说，邮费不算实质性影响，合同成立且合同含有包邮。
Apple writes to Microsoft: "If your company buys AirPods Max, it's only $500 a pair." Microsoft replies: "We are willing to buy a pair for $500 with free shipping." Apple immediately objects to the free shipping term. A contract is formed, but it does not include the free shipping term.
苹果给微软写信：如果贵司买AirPods Max，只需要500美金一副。微软回复：愿意500美金包邮买一副。苹果立刻反对包邮的条款。合同成立且不含有包邮条款。
Microsoft writes to Apple: "We will purchase 100 pairs of AirPods Max for $500 each." Apple replies: "Agreed, but at this price, the headphones come with no warranty." Even if Microsoft does not promptly object to the no-warranty term, disclaiming warranty liability materially alters the contract terms. Unless Microsoft explicitly agrees to waive the warranty obligation, a contract of sale with a warranty is formed.
微软给苹果写信：500美金采购100副AirPods Max。苹果回复：同意，但这个价格的耳机没有任何保修。即使微软没有及时反对没有保修的条款，免除自己的质保责任也实质性修改了合同的条款，除非微软明确同意免除对方的质保义务，否则成立的是有质保的买卖合同。
Microsoft writes to Apple: "Purchasing 100 pairs of AirPods Max for $500 each." Apple replies: "Agreed, but any disputes must be resolved through arbitration." Here, multiple factors must be considered, such as whether resolving disputes through arbitration is already an industry custom. Exam questions will not directly ask you for the answer, but they might ask what the determinative factor is for whether the arbitration clause becomes part of the contract: the answer is whether the arbitration clause materially alters the terms of the offer.
微软给苹果写信：500美金采购100副AirPods Max。苹果回复：同意，但任何争议必须走仲裁。这里要考察多种因素，比如通过仲裁解决争议是否本来就是行业惯例。考题不会直接要你给出答案，但可能会问你仲裁条款会不会成为一部分的决定性因素是什么：答案是仲裁条款有没有实质性修改了（materially alter）要约的条款。
Apple writes to Microsoft: "If your company buys AirPods Max, it is only $500 per pair, shipping not included." Microsoft replies: "Willing to buy one pair, but shipping must be included." A contract is formed. The majority view holds that neither party's terms regarding shipping should be adopted; instead, the UCC's gap-filler provisions for shipping in this type of transaction should be referenced.
苹果给微软写信：如果贵司买AirPods Max，只需要500美金一副，不包邮。微软回复：愿意买一副，但必须包邮。合同成立。多数说认为双方关于包邮的条款都不应采纳，而是参考UCC中对于此种交易类别的邮费规定。
Apple writes to Microsoft: "If your company buys AirPods Max, it is only $500 per pair," and the letter also details various terms related to delivery. Microsoft replies: "I agree to all the terms of the contract, and am willing to buy one for $400." Here, the parties have not reached mutual assent on a material term of the contract, so no contract is formed.
苹果给微软写信：如果贵司买AirPods Max，只需要500美金一副，信中还事无巨细地规定了各种和交付有关的条款。微软回复：合同的所有条款都同意，愿意400美金买一台。这里双方没有就合同的关键条款达成合意，合同不成立。
UCC：直接发货UCC: Direct Shipment
Direct shipment is treated by the UCC as an acceptance of an offer. By comparison, under the common law, direct performance is also treated as an acceptance of an offer.
直接发货被UCC视为接受要约。作为对比，在普通法下直接履行也视为接受要约。
A buyer orders 1,000 parts, and a contract is deemed formed at the same time the seller ships the 1,000 parts.
买家订购1000个零件，卖家发货1000个零件的同时视为合同成立。
However, in exam questions, the seller often will not ship according to the buyer's request. If the shipped goods differ from the offer, it is deemed both an acceptance of the contract and a breach.
但题目中卖家不会按照买家的要求发货。如果发货的内容和要约不同，视为接受合同的同时违约。
A buyer orders 1,000 red parts, and the seller ships 1,000 blue parts; this is deemed both an acceptance of the contract and a breach. The buyer may reject the goods, accept a portion, or accept all of them, and under any of these choices, still claim damages.
买家订购1000个红色零件，卖家发货1000个蓝色零件的同时视为接受合同和违约。买家可以拒收、收一部分、全收，并且在任一种选择下，依然主张损害赔偿。
Unless the seller seasonably notifies the buyer that the shipment of non-conforming goods is offered only as an accommodation to the buyer. In this case, it is not deemed a breach, but rather a counteroffer, which the buyer may choose to accept or reject.
除非卖家在合理时间内通知买家将要寄出不是完全符合要约的商品，也称作替代安排（accommodation），此时不视为违约，而是反要约（counteroffer），买家可以选择接受或者拒绝。
A buyer orders 1,000 red parts. The seller ships 1,000 blue parts and notifies the buyer that red parts are out of stock and blue parts are temporarily sent as a substitute. This is a counteroffer to trade blue parts. If the buyer accepts the blue parts, a contract for the blue parts is deemed formed. If the buyer rejects the blue parts, no contract is formed, and the seller has the right to reclaim the blue parts.
买家订购1000个红色零件，卖家发货1000个蓝色零件并通知甲红色零件缺货，暂用蓝色零件代替。这是交易蓝色零件的反要约。买家如果接受蓝色零件，视为成立蓝色零件的合同。买家如果拒绝蓝色零件，则没有成立合同，卖家有权要回蓝色零件。
Sometimes the trap in exam questions is that the contract has already been formed. Even if the seller notifies the buyer of an accommodation at the time of shipping non-conforming goods, it is still deemed a breach, not a counteroffer.
有时候题中的陷阱在于合同早已经成立，即使寄出不符合要求商品的同时通知买家作出了替代安排，仍然视为违约，而不是反要约。
A buyer orders 1,000 red parts, and the seller promises to ship within 3 days. Later, the seller notifies the buyer that red parts are out of stock, temporarily substitutes them with blue parts, and ships the blue parts. If the seller had not promised to ship within 3 days, the contract would not have been formed; however, since the contract was already formed when the seller promised to ship, the failure to ship red parts constitutes a breach.
买家订购1000个红色零件，卖家承诺3天内发货。后通知买家红色零件缺货，暂用蓝色零件代替并发货蓝色零件。若不是卖家承诺3天内发货，合同没有成立，但卖家承诺发货时合同已经成立，无法发货红色零件构成违约。
合同的有效性和可执行性Validity and Enforceability of Contracts
对价Consideration
对价理论Consideration Theory
It is inappropriate for courts to enforce gift contracts because the rights and obligations of the parties are not reciprocal. Chinese law provides for real contracts and consensual contracts, and also grants the donor an arbitrary right of revocation before the actual gift is made. Thus, courts theoretically do not intervene in the enforcement of gift contracts, unless it is a gift involving a moral obligation.
让法院来执行赠与合同是不合适的，因为双方的权利义务并不对等。中国的法律规定了实践合同和诺成合同，还赋予赠与方在实际赠与之前的任意撤销权。这样法院从理论上不介入赠与合同的执行：除非是负有道德义务的赠与。
The common law system has a complete theory of consideration, which is not only used to handle gift issues. For example, as mentioned earlier, an irrevocable offer under the common law must be supported by consideration.
英美法系有一套完整的对价（consideration）理论，不仅仅是用来处理赠与问题。比如前文中所述普通法中不可撤销的要约就必须要由对价支持。
More generally, all contracts must be supported by consideration; otherwise, no contract is formed at all.
更一般地，所有合同都必须有对价支持，否则合同根本不成立。
A promises to gift B 10,000 yuan, and B agrees. Here, there is mutual assent, so a contract is formed. However, if A fails to deliver and B sues in court, the contract will be unenforceable due to a lack of consideration.
甲承诺赠与乙10000元，乙同意，这里有了合意，所以合同成立。但如果甲没有交付，乙起诉到法院，合同会因为没有对价而无法执行。
Consideration can be an affirmative act (performance) or a negative forbearance. The consideration exchanged by the parties can be highly disproportionate, but it cannot be merely nominal consideration or an illusory promise.
对价可以是积极的行为（performance），也可以是消极的忍受（forbearance）。合同双方的对价可以很悬殊，但不能只是象征意义的对价或者是虚无的承诺（nominal consideration）。
A and B agree to a transaction for land worth $100,000 for $1. Here, the $1 is merely nominal, and the contract is unenforceable.
甲和乙成立价值10万的土地1元成交。这里1元只有象征意义，合同无法执行。
A and B agree to a transaction for land worth $100,000 for $10,000. Although the consideration does not reflect the actual value of the land, it is not nominal consideration, and the contract is enforceable.
甲和乙成立价值10万的土地1万元成交。虽然对价不能反映土地的实际价值，但并不是虚无的对价，合同可以执行。
A and B enter into an option contract, agreeing that for the price of $1, A will keep an offer to sell Blackacre for $100,000 open for 24 hours. As above, courts do not inquire into the adequacy of consideration; they merely seek to avoid nominal consideration. For keeping an offer open for 24 hours, a consideration of $1 may be sufficient, and a court would be inclined to enforce this option contract.
甲和乙成立option contract，约定以1美元的价格，让甲保留以10万美元出售黑土地的要约24小时。同上，法院并不决定对价是否足够，仅仅是为了避免虚无的对价。对于将要约保留24小时来说，1美元的对价可能是足够的，法院会倾向于执行这个option contract.
A says to B, "If you come to my house, I will give you an antique." B spends thousands of dollars taking a business class flight to A's house. Although B incurred significant expenses, it provided no benefit to A and is not consideration; the contract is unenforceable.
甲对乙说，你要来我家，我就送你一件古董。乙花费数千美元，搭乘商务舱来到甲家里。虽然乙花费不菲，但对甲没有任何好处，不是对价，合同无法执行。
A father says to his daughter: "If you do not smoke before you turn 18, I will give you $1,000." Consideration can be not only an affirmative act but also a negative forbearance, and the daughter's forbearance is for the father's emotional satisfaction (it does not need to be an economic benefit); the contract is enforceable.
爸爸对女儿说：如果你18岁之前不抽烟，我就给你1000元。对价不仅也可以是积极的行为，也可以是消极的忍受，且女儿的忍受是为了爸爸情绪上的满足（不必是经济利益），合同可以执行。
A and B sign a contract to purchase "any quantity of parts A decides." A and B sign a contract, but A retains an "arbitrary right of revocation." A and B sign a contract, but it only takes effect "when A deems it necessary." All three of the above contracts are unenforceable because they are illusory promises.
甲和乙签订合同购买“甲决定的任何数量”的零件。甲和乙签订合同但甲享有“任意撤销权”。甲和乙签订合同但只有“甲认为有必要时”合同才生效。以上三个合同都因为是虚无的承诺而无法执行。
A and B sign a contract to purchase all the parts "A requires this year." A and B sign a contract to purchase all the parts "B produces this year." The contracts are enforceable. We call the former a requirement contract, and the latter an output contract.
甲和乙签订合同购买“甲今年需要的”所有零件。甲和乙签订合同购买“乙今年生产的”所有零件。合同可以执行。我们把前者称作全需求合同（requirement contract），后者叫做全产出合同（output contract）。
A and B sign a contract to purchase all the parts "A requires this year," and B has sufficient production capacity. Midway through, A decides to use 20% of parts produced by C. A is in breach of contract.
甲和乙签订合同购买“甲今年需要的”所有零件，乙产能充足。甲中途决定选用20%丙生产的零件，甲构成违约。
A and B sign a contract to purchase all the parts "A requires this year," and B has sufficient production capacity. Midway through, A's client insists that a certain product use parts produced by C, so A purchases a small amount of parts from C. This may not constitute a breach at all, because in a requirements contract, the buyer's "requirements" are subject to the duty of good faith. If the client mandates the use of C's parts, A has no "requirement" for B's parts for that portion, so purchasing C's parts is in compliance with the contract.
甲和乙签订合同购买“甲今年需要的”所有零件，乙产能充足。中途甲的客户执意要求某产品使用丙生产的零件，甲因此购买了少量丙的零件。这可能根本不构成违约，因为在全需求合同中，买方的“需求”受诚实信用（good faith）原则约束。如果客户强制要求使用丙的零件，甲对乙的零件在这一部分就没有“需求”，因此购买丙的零件是符合合同的。
Consideration cannot be a past act. A promise to pay a debt barred by the statute of limitations is an exception to the consideration requirement, rather than using the time-barred debt as consideration. The majority view holds that to enforce such a promise, the new agreement requires a writing, partial performance, or that the creditor has made arrangements based on reliance.
对价不能是过去的行为。承诺偿还已过诉讼时效（statute of limitations）的债务是对价原则的例外，而不是把经过诉讼时效的债务作为对价。多数观点认为，如果要执行这种承诺，新的约定需要书面、部分履行，或债权人基于信赖作出了安排。
A gifts and delivers an expensive book to B. B says, "This book is too expensive; I still must pay you for it." The next day, B changes his mind. A cannot enforce the payment for the book.
甲赠送并交付给乙一本昂贵的书，乙说，这本书太昂贵了，我还是得把书钱付给你。第二天乙反悔，甲无法执行书钱。
A doctor saves a patient's life. After paying the medical bills in full, the patient, out of gratitude, promises to pay the doctor $10,000 every year thereafter. Because the act of saving the life occurred in the past, the subsequent gratitude payments are unenforceable due to a lack of consideration.
医生救活了病人，病人付清医药费后为了感谢医生，承诺以后每年付给医生一万元。因为救人的行为发生在过去，所以之后的感谢费因没有对价而无法执行。
A debtor and a creditor agree that a debt from ten years ago will be paid off next month. Although the debt has long passed the statute of limitations, the new contract is enforceable.
债务人和债权人约定十年前的一笔债务下个月还清。虽然该债务早就过了诉讼时效，但新的合同可以执行。
Consideration can involve risk, but if one party knows that the purported consideration is actually completely worthless, the contract is unenforceable.
对价可以有风险，但如果其中一方知道所谓的对价其实完全没有价值，合同无法执行。
After their parents pass away, two brothers agree that they will equally divide whatever inheritance their parents leave them. Neither brother knows that the parents have already left the entire inheritance to the older brother, but the "possibility of receiving an inheritance" is valid consideration.
父母去世后，兄弟约定无论父母留给他们什么遗产，他们都将平分。兄弟都不知道父母已经把遗产全部留给了哥哥，但“分得遗产的可能”是有效的对价。
After their parents pass away, two brothers agree that they will equally divide whatever inheritance their parents leave them. However, the younger brother knows that the parents have already left the entire inheritance to the older brother. The contract is unenforceable due to a lack of consideration.
父母去世后，兄弟约定无论父母留给他们什么遗产，他们都将平分。但弟弟知道父母已经把遗产全部留给了哥哥。合同因没有对价而无法执行。
A driver hits an accountant. The accountant says: "If you give me $500, I won't sue you." The driver agrees. In reality, the accountant does not have a valid cause of action, but the accountant genuinely believes he can sue the driver. The consideration is valid.
司机撞到了会计，会计说：如果你给我500块钱，我就不告你。司机同意。实际上会计并没有有效的案由，但会计真心相信自己可以起诉司机。对价有效。
A driver hits a lawyer. The lawyer says: "If you give me $500, I won't sue you." The driver agrees. In reality, the lawyer does not have a valid cause of action, and the lawyer knows this. The lawyer has not provided any consideration, and the contract is unenforceable.
司机撞到了律师，律师说：如果你给我500块钱，我就不告你。司机同意。实际上律师并没有有效的案由，律师也知道这一点。律师没有提供任何对价，合同无法执行。
已经存在的法律义务Pre-existing Legal Duty
If a party to a contract already has a certain duty before the contract is formed (pre-existing duty), this duty cannot serve as new consideration. This duty may be a duty imposed by law or a duty stipulated by a contract.
如果合同一方在合同成立之前已经有了某个义务（pre-existing duty），不能把这个义务作为新的对价。该义务可能是法律规定的义务，也可能是合同约定的义务。
A offers a $10 million reward for the rescue of his kidnapped daughter, and a police officer successfully rescues her. Because the police officer already had a pre-existing duty to rescue the daughter, the officer cannot enforce this unilateral contract.
甲悬赏1000万营救被绑架的女儿，警察成功救出女儿。因为警察本来就有营救女儿的义务，警察无法执行这个单方合同。
What we need to remember are the exceptions to this rule.
我们要记的是这个原则的例外。
A singer charges $1 million to perform songs. Before the show, the parties negotiate to adjust the fee to $1.2 million, with the songs remaining the same. The modification of the contract is not supported by new consideration and is unenforceable. However, the lack of consideration merely makes the new $200,000 unenforceable; if the promoter transfers $1.2 million on the spot and the singer finishes the performance, the promoter cannot recover the extra money.
歌手收取100万演唱歌曲，开演之前双方协商费用调整为120万，歌曲不变。合同的修改没有新的对价支撑，无法执行。但没有对价仅仅是让新的20万无法执行，如果演出商现场打款120万，歌手唱完后，演出商也无法追回。
Before the show, the parties negotiate to adjust the fee to $1.2 million and change the performance to another seemingly simpler song. The modification of the contract is valid.
开演之前双方协商费用调整为120万，改唱另一首似乎更简单的歌曲，合同的修改有效。
Before a concert, a singer demands a price increase, but the parties fail to reach an agreement on adjusting the fee. A fanatic fan of the singer voluntarily offers 200,000 to have both parties perform the original contract. The singer performs as scheduled. As to the fan, the singer originally had no contractual obligation to sing for them, so the fan's promise to pay 200,000 is enforceable.
开演之前歌手要求涨价，双方协商调整费用未果。歌手的狂热粉丝自愿出资20万让双方履行原合同。歌手如期履行。对粉丝来说，歌手原本没有唱歌的合同义务，粉丝的20万可以执行。
Before a daughter buys a car on credit from a dealership, the dealership discovers her poor credit history and requires her father to act as a guarantor. The three parties sign an agreement. The guaranty is enforceable.
女儿在车商贷款买车前，车商发现女儿的信用记录很差，于是要求父亲担保，三方签署协议。担保可以执行。
After a daughter buys a car on credit from a dealership, the dealership discovers her poor credit history and requires her father to act as a guarantor. For the father, becoming a guarantor involves no new consideration, so the guaranty is unenforceable.
女儿在车商贷款买车后，车商发现女儿的信用记录很差，于是要求父亲担保。对父亲来说，成为担保人没有获得任何新的对价，担保无法执行。
During a concert, security guards hired by the organizer threw away fans' light signs, causing a severe negative impact. After the concert, the singer threatens to sue the organizer. The organizer agrees to increase the performance fee by 200,000 in exchange for the singer's forbearance to sue. The new promise for 200,000 is enforceable.
演唱会时主办方聘用的保安丢掉了粉丝的灯牌造成恶劣影响，会后歌手威胁要起诉主办方，主办方同意增加20万演出费换取歌手不起诉，新的20万可以执行。
The concert was clearly a great success, but the organizer unreasonably picks a fight to reduce the performance fee by 200,000. The singer, desperate for money, reluctantly accepts the reduced fee. If the singer can prove that the organizer's dispute was fabricated (not in good faith), the singer can sue to recover the deducted 200,000.
演唱会明明开的非常成功，但主办方非要找茬要减少20万演出费，歌手缺钱无奈收下少了20万的演出费。如果歌手能证明主办方的纠纷是编造的（不真诚），可以起诉要回少给的20万演出费。
Before a concert, a pandemic breaks out, and the singer needs to quarantine for 14+7 days before continuing the concert. The organizer agrees to increase the performance fee by 200,000. The new promise for 200,000 is enforceable.
演唱会前疫情爆发，歌手需要隔离14+7天才能继续演唱会，主办方同意增加20万演出费，新的20万可以执行。
A pays B to cut down a tree in A's yard. During the cutting, B encounters a beehive, and the parties agree to increase the fee. Because a beehive is foreseeable and easily observable before signing the contract, it does not constitute an unforeseen circumstance, and the promise to pay the increased fee is unenforceable.
甲支付乙砍掉自己院子中的树，砍伐过程中遇到蜂巢，双方约定增加费用。由于蜂巢是可以预见到也很容易在签约前观察到的事务，不属于不可预见的情况，增加的费用不可执行。
A gas station and an oil supplier sign a 5-year contract setting the oil price at 6 yuan per liter. In the third year, international oil prices rise, and continuing to perform the contract would cause unreasonable hardship for the supplier. The parties agree to adjust the price to 6.5 yuan per liter. Because this adjustment is made in good faith, it is enforceable without consideration.
加油站和供油商签订5年的合同约定油价为6元一升，第三年国际油价上涨，继续履行合同对供油商会造成不合理的困难，双方约定油价调整为6.5元一升，因为该调整基于善意，可以没有对价。
During the construction of a house by a builder, international cement prices rise, and the parties agree to increase the construction fee by 1 million. A normal increase in cement prices is not an unforeseeable circumstance for both parties. Moreover, construction contracts are governed by common law, where good faith alone is insufficient. The contract modification will be unenforceable due to a lack of consideration.
建筑商在建房的过程中，国际水泥价上涨，双方约定将建房费用增加100万。水泥价格的正常上涨并不属于双方都无法预料到的情况，且建筑合同适用普通法，仅有善意是不够的。合同的修改会因为没有对价而无法执行。
A owes B 800,000, due on December 31. The parties negotiate and agree that if A pays before September 1, a payment of 600,000 will satisfy the debt in full. Early repayment constitutes new consideration.
甲欠乙80万，约定12月31日还款。双方协商决定9月1日之前还款只用还60万即可还清。提前还款是新的对价。
反欺诈法Statute of Frauds
反欺诈法的范围Scope of the Statute of Frauds
To prevent fraud, the Statute of Frauds (SOF) requires certain contracts to be in writing; otherwise, they are unenforceable. The SOF is not a common law principle but an ancient English law. However, because it was widely adopted at the time of the founding of the United States, it remains in general use today.
为了防止诈骗，反欺诈法（Statute of Fraud，SOF）规定特定的合同必须以书面订立，否则无法执行。反欺诈法并不是普通法原则，是古老的英国的法律，但因为美国建国时就普遍存在，所以现在普遍沿用。
We need to memorize the first 5 types of contracts subject to the SOF, while the latter 3 types are rarely tested.
我们需要前5类适用反欺诈法的合同烂熟于心，而后3类并不常考。
A writing does not mean every detail must be specified. For contracts for the sale of goods, as long as the quantity is in writing, the contract is enforceable. If the price is not agreed upon, it can be supplied by UCC gap-filler rules. However, if evidence shows that the parties had a dispute over the price, the contract would not have been formed at all due to a lack of mutual assent.
书面并不意味着要规定地事无巨细。对物品买卖合同而言，只要数量是书面的，合同就可以执行。价格没有约定可以用UCC的规则补足。但如果证据显示双方关于价格有分歧，那合同会因为没有合意而根本没有形成。
A and B agree to build a fence for a house the year after next. Although building the fence only takes a few weeks, because the contract's expected completion is more than one year after signing, it must be in writing.
甲和乙约定后年给房子修一个篱笆，虽然修篱笆只需要数周时间，但因为合同预期完成时超过签约后一年，所以需要书面签订。
A and B sign a lifetime employment contract (lifetime, permanent, indeterminate). Because the employee could die within a year (and death represents full performance of a "lifetime" contract), it does not require a writing.
甲和乙签订终身雇佣合同（life time, permanent, indeterminate），但因为雇员可能在一年内死亡（死亡即代表“终身”合同的完全履行），所以不需要书面签订。
A gives B a 1-year employment offer. After thinking about it for 2 months, B directly starts working. This contract is enforceable without a writing because the contract was formed on the day B started working (accepting the offer by conduct), and it can be fully performed in exactly one year.
甲给乙1年的招工要约（offer），乙思考2个月后直接开始上班。该合同不需要书面也可以执行，因为合同是在乙开始工作当天成立的（通过行为接受要约），且刚好一年可以履行完毕。
A nephew drives his own car to get it cleaned. The car wash calls his uncle, and the uncle says: 'Put the car wash fee on my account.' This is a service contract directly between the uncle and the car wash, and it obviously can be fully performed within one year, so it does not require a writing.
侄子开着自己的车去做清洁，洗车行给叔叔打电话，叔叔说：洗车钱算我账上。这是叔叔直接和洗车行签订的服务合同，且显然有可能在一年内履行完毕，不需要书面。
A nephew drives his uncle's car to get it cleaned. The car wash calls the uncle, and the uncle says: 'If he cannot pay, I will pay.' This is a suretyship contract, but because the car wash is for the uncle's own benefit, this suretyship contract does not require a writing.
侄子开着叔叔的车去做清洁，洗车行给叔叔打电话，叔叔说：如果他付不出钱，我来付。这是担保合同，但因为洗车是为了叔叔的利益，所以该担保合同不需要书面。
You can use the mnemonic MY LEGS to remember the first 6 most common situations:
可以用MY LEGS来记忆前6种最常见的情形：
满足反欺诈法的格式Formats Satisfying the Statute of Frauds
A 'writing' can be on paper or in electronic form, such as a fax, email, text message, or instant messaging app.
“书面”可以是纸质，也可以是电子形式，比如传真、电子邮件、短信、即时通讯软件。
A 'signature' can be a personalized signature, initials (e.g., Joe Biden initialized as JB), a stamp, or an electronic signature. Under UCC rules, a document sent on company letterhead also constitutes a valid signature.
“签名”可以是个性签名，简签（initial, 比如乔·拜登简写成JB），盖章，电子签名。在UCC规则下，用公司的抬头纸发出也是有效的签名。
If the parties' contract consists of several documents and only one is signed, but the other documents are clearly part of the same transaction as the signed document, it also satisfies the Statute of Frauds.
如果双方的合同有好几份文件，只有一份有签名，但其他文件明显和签名的文件是一个系列，也符合反欺诈法的要求。
Please note that we only require the signature of the defendant; it does not matter if the plaintiff (the party raising the dispute) has not signed. This is a frequently tested trap in exam questions.
请注意，我们只要求有被告的签名即可，原告方（提出争议的人）没有签名则无所谓。这是题目中常考的陷阱。
A writes a letter to B: 'I will sell you my car for $5,000,' and A signs the letter. B calls A to accept the offer. Later, A backs out, and B sues A in court. Although B did not sign, A signed as the defendant, so the contract is enforceable against A.
甲给乙写信：我把我的车5000美金卖给你，甲在信上签名。乙致电甲接受要约。后甲反悔，乙诉至法院。虽然乙没有签名，但甲作为被告签了名，合同可以执行。
反欺诈法的例外Exceptions to the Statute of Frauds
The Statute of Frauds encourages parties to put their transactions in writing to avoid a flood of oral contracts and conflicting testimonies in court. However, since the Statute of Frauds ultimately regulates legal relationships involving private rights, if the defendant does not actively invoke the Statute of Frauds as a defense, the court will not intervene on its own to declare the contract unenforceable.
反欺诈法鼓励大家把交易用文字确定下来，避免口头合同泛滥而在法庭上各执一词。但反欺诈法调整的毕竟是私权利之间的法律关系，如果被告不主动援引反欺诈法，法庭不会主动介入而宣布合同无法执行。
We will learn in Civil Procedure that if the Statute of Frauds defense is not asserted at the outset, it is deemed waived. Similarly, if the defendant admits the existence of the contract, it is deemed to satisfy the Statute of Frauds.
我们会在民诉中学到，如果不一开始主张反欺诈法的抗辩，那么视为放弃该抗辩。同样，如果被告承认了合同的存在，则视为符合反欺诈法的要求。
In addition, for service contracts, if one party has fully performed, the contract is deemed to satisfy the Statute of Frauds. However, partial performance is not an exception to the Statute of Frauds; the performing party can only claim reasonable reliance damages under equity.
除此之外，服务合同如果一方已经全部履行完毕，则合同视为符合反欺诈法的要求。但部分履行不是反欺诈法的抗辩，只是可以依据衡平法主张合理信赖的损失。
A orally asks B to build a house for A, with a construction period of one and a half years. Half a year later, A backs out, and B stops working. Here, B has only partially performed the contract, so the contract is unenforceable, and B cannot claim expectation damages for breach of contract. However, B may be able to claim reasonable reliance damages based on equity.
甲口头要求乙给甲盖一个房子，工期一年半。半年后甲反悔，乙遂停工。这里乙只是部分履行合同，所以合同无法被执行，乙不能主张违约损失。但可能可以基于衡平法主张合理的信赖损失。
A and B orally sign a 13-month employment contract. After A works for 4 months, B fires A. Although A cannot enforce the remaining 9 months, A can demand that B pay reasonable compensation for the 4 months worked.
甲、乙口头签订13个月的雇佣合同，甲工作4个月后乙开除甲。虽然甲无法要求执行剩下的9个月，但甲可以要求乙给付4个月的合理报酬。
The UCC has similar rules. Even if the parties do not have a written contract, if the seller has received payment or the buyer has received and accepted the goods, or if the goods are specially manufactured for the buyer, the Statute of Frauds is deemed satisfied.
UCC有类似的规定，双方虽然没有书面合同，但如果卖家已经收款/买家已经收货，或者物品是为买家定做的，则视为满足了反欺诈法的要求。
A buyer and a seller agree to trade 1,000 parts for $10,000. The seller delivers 500 parts to the buyer on the spot, and the buyer accepts them. The contract is enforceable to the extent of the 500 parts.
买卖双方约定以10000美金的价格交易1000个零件，卖家当场交付给买家500个零件，买家收下，在500个零件的范围内合同可以执行。
A buyer and a seller agree to trade a used car for $10,000. The buyer pays the seller $2,000 on the spot. Because the car cannot be apportioned, the entire contract is enforceable.
买卖双方约定以10000美金的价格交易一辆二手车，买家当场支付给卖家2000美金，因为车无法被分割，整个合同可以执行。
Mr. Zhong orally asks a painter to paint a 'Painted-Face Monkey' for him, promising to pay $1,000 upon completion. After the painter starts working, Mr. Zhong backs out. If viewed as a unilateral contract, the offer becomes irrevocable once performance begins. If considering the Statute of Frauds, because the portrait is specially manufactured for Mr. Zhong, the contract satisfies the Statute of Frauds, and the entire contract is enforceable.
钟老师口头要求画家给他画一幅《花脸猴》，完工后支付1000美金。画家开工后钟老师反悔。如果视为单方合同，开工后要约不可撤回。如果考虑反欺诈法，因为画像是为钟老师定做的，合同满足反欺诈法的要求，整个合同可以执行。
The UCC has another special rule: if both parties are merchants, even without a written contract, if one party promptly sends a written confirmation of their oral agreement to the other party, and the receiving party does not object in writing within 10 days, it is deemed to satisfy the Statute of Frauds. However, the writing must be signed to be enforceable against the drafter (sender); otherwise, it cannot be used against the recipient either.
UCC还有一个特殊的规定，双方如果都是商家，虽然没有书面合同，但如果一方把口头合意及时以书面形式送达给对方，对方没有在10天内提出书面反对，视为满足反欺诈法的要求。但书面形式必须有签名用来针对起草方（发出方），否则也无法用来针对被送达方。
A buyer calls a seller to order 3 tons of crayfish. The seller faxes the agreed quantity, price, and delivery method to the buyer on company letterhead. After receiving the fax, the buyer does not object in writing within 10 days. The contract is enforceable.
买家向卖家打电话订购3吨小龙虾，卖家将商量好的数量、价格、送达方式等用有公司抬头的传真发给买家，买家收到传真后没有在10天内提出书面反对。合同可以执行。
Buyer calls Seller to order 3 tons of crawfish. Seller writes down the agreed quantity, price, and delivery method on a blank piece of paper and sends it to Buyer, but without a signature. Because this piece of paper cannot be used against Seller (as it lacks a signature), it likewise cannot be used against Buyer. Even if Buyer fails to object in a timely manner, the contract remains unenforceable.
买家向卖家打电话订购3吨小龙虾，卖家将商量好的数量、价格、送达方式等用一张白纸写下来送给甲方，但没有签名。因为这个白纸无法用来针对卖家（没有签名），所以也同样无法用来针对买家。即使买家没有按时提出反对，合同依然无法执行。
其他抗辩Other Defenses
无效合同，可撤销的合同和无法执行的合同Void, Voidable, and Unenforceable Contracts
Similar to Chinese contract law, we sometimes need to distinguish between contracts that are void ab initio and those that are voidable, and there is even an additional category: "unenforceable contracts."
和中国的合同法一样，我们有时候需要区分自始无效的合同和可撤销的合同，甚至还多了一个“无法执行的合同”。
If there is no valid offer or effective acceptance, the contract was never formed in the first place. It is treated as if no contract exists. Similar to this is a "void contract," along with a familiar catchphrase: "a void contract is void ab initio." We use void ab initio to mean void from the beginning; ab initio is Latin for "from the beginning."
如果没有有效的要约，或者没有被有效地接受，那么一开始合同就没有成立。视为没有合同。类似的还有“无效的合同”，以及一句似曾相识的口头禅：“无效的合同自始无效”。我们用void ab initio表示自始无效，ab initio是拉丁语“从一开始就”的意思。
A voidable contract is similar to the Chinese definition, even identical in that only the protected party has the power to void it.
可撤销的合同（voidable）和中国的定义差不多，连只有受保护的一方可以撤销都如出一辙。
An unenforceable contract is a new concept. We have learned that a contract that does not comply with the Statute of Frauds, although valid, is unenforceable. The difference between it and void or voidable contracts is that if it has already been fully performed, it cannot be undone. It should be noted that the essence of a contract is consideration; without consideration, there is no contract. The essence of a deed, however, is form; with a deed, consideration is not required.
无法执行的合同是新事物，我们已经学到，不符合反欺诈法的合同虽然有效，但无法执行。它和合同无效、合同可撤销的区别在于，如果已经执行完毕，不可反悔。需要注意的是，合同的本质是对价，没有对价就没有合同。而契约（deed）的本质是形式，有了契约，可以不用对价。
A sells a book worth less than $1 to B for $10,000. Both parties deliver the book and a money order (or bank draft). Under the consideration theory, this is clearly a gift disguised as a sale with the book as nominal consideration, resulting in no contract being formed. However, since the book and money order have already been delivered, this constitutes a completed gift and therefore cannot be undone. Under the Statute of Frauds theory, the sale of goods for $500 or more requires a writing; the Statute of Frauds is a contract enforceability theory that applies on the premise that a contract has been formed. If unperformed, one party cannot sue the other for specific performance. If it were a check, a party might still notify the bank to cancel it, but a bank draft is payable on sight and is equivalent to cash.
甲将一本价值不到1美元的书以10000美元出售给乙，双方交付了书和本票（money order, bank draft）。如果用对价理论，这显然是以一本书的对价为名行赠与之实，是虚无的对价（nominal consideration），导致合同未成立。但既然书和本票已经交付，这构成了一个已完成的赠与（completed gift），因此无法反悔。如果用反欺诈法理论，500美元以上的货物买卖需要书面，反欺诈法是合同可执行性理论，适用于合同成立的前提下。如果没有履行，一方无法起诉对方强制履行。如果是支票，一方或许还可以通知银行取消，但本票银行见票即付，等同于现金。
Assuming the above contract is void or voidable (e.g., formed under duress), a party could demand the return of the $10,000; of course, the book must also be returned.
假设上述合同是无效的或者可撤销的（比如，通过胁迫订立的合同），一方就可以要求返还10000美元：当然，书也要还回去。
Later we will also learn that an unconscionable contract is also unenforceable.
后面我们还会学到，不合情理（unconscionability）的合同也是无法执行的。
Essay Tip: Almost all California contract essay questions start by discussing the applicable law. Take the official selected answer B for Q2 of the 2021 California Bar Exam as an example:
论文技巧： 加州几乎所有的合同写作题都以讨论法律适用为开头。以加州2021年Q2官方精选答案B为例：
Where a contract is for a sale of goods, Article 2 of the UCC applies. For all other types of contracts, the common law applies. Here, the contract was for Bright Earth Solutions (B) to purchase a commercial tractor mower from SM. This is a contract for a sale of goods, therefore Art. 2 of the UCC applies to the contractual analysis set out below.
Where a contract is for a sale of goods, Article 2 of the UCC applies. For all other types of contracts, the common law applies. Here, the contract was for Bright Earth Solutions (B) to purchase a commercial tractor mower from SM. This is a contract for a sale of goods, therefore Art. 2 of the UCC applies to the contractual analysis set out below.
After discussing the applicable law, contract formation (including mutual assent and consideration) is usually discussed next. Then, whether the contract is enforceable (Statute of Frauds), and whether there are any defenses that make the contract void or voidable.
讨论完适用法律后，通常会紧接着讨论合同成立（包括合意 mutual assent 和对价 consideration）。接下来讨论合同是否可执行（反欺诈法），以及是否有导致合同无效、可撤销的事由。
New York State does not need to strictly follow this; the main focus is on answering the question correctly.
纽约州则不必拘泥于此，以答对问题为主。
事实认识错误（Mistake）Mistake
Mistake means an erroneous belief about a fact, which can be written in the contract or not.
Mistake的意思是对事实认识的错误，该事实可以写在合同中，也可以不在合同中。
A and B enter into a contract to refuel a California-licensed car with the license plate NTGUILTY. Unknown to both parties, it is a new energy electric vehicle. This is a mistake of fact not written in the contract.
甲乙签订给一辆车牌为NTGUILTY的加州牌车加油的合同，双方都不知道的是，这是一辆新能源电车。这是不在合同中的事实认识错误。
A and B enter into a contract to refuel a California-licensed car with the license plate NTGUILTY, and the contract specifies that it is a gasoline car. But unknown to both parties, it is actually a new energy electric vehicle. This is a mistake of fact written in the contract.
甲乙签订给一辆车牌为NTGUILTY的加州牌车加油的合同，合同中注明了这是一台汽油车。但双方不知道的是，这其实是一台新能源电车。这是写在合同中的事实认识错误。
A unilateral mistake usually cannot rescind a contract, unless:
单方面的事实认识错误（unilateral mistake）通常不可以解除合同，除非：
Then the adversely affected party can void the contract (voidable).
那么受影响的一方可以撤销合同（voidable）。
A salesperson mistakenly sells a $45,000 car to a customer for $40,000. The customer is unaware of the mistake, and the contract price is $40,000.
销售误把一辆45000元的车以40000元的价格出售的客户，客户并不知情，合同价格为40000。
A salesperson mistakenly sells a $45,000 car to a customer for $5,000. Before the customer significantly relies on the mistake, the contract can be rescinded.
销售误把一辆45000元的车以5000元的价格出售的给客户，在客户没有显著依赖该错误的时候，合同可以解除。
Corresponding to unilateral mistake is mutual mistake. If a mutual mistake materially affects the contract, the adversely affected party can void the contract (voidable by the adversely affected party), provided they did not bear the risk of the mistake.
和单方面误解（unilateral mistake）相对应的是共同误解（mutual mistake）。共同误解如果实质性影响到合同，受影响的一方在没有承担该错误风险的情况下，可以撤销合同（voidable by the adversely affected party）。
The refueling contracts in the previous two examples can both be voided due to mutual mistake.
前面两个例子中的加油合同都可以因为共同误解被撤销。
A buyer purchases an antique that appears worthless for $1,000 at an antique market, later discovering it is worth $1 million. Both parties to the transaction should recognize the risks of antique trading, so there is no mutual mistake.
买家在古玩市场以1000元购买一件看起来一无所值的古玩，后发现价值100万，交易双方应当认识到古玩交易的风险，不存在共同误解。
The buyer and seller have an antique appraised and trade it for $1,000. Unknown to both parties, the appraiser made a mistake, and the gem is actually worth $1 million. The appraisal result is a mutual mistake of both parties. Sending it for appraisal indicates that the parties did not intend to bear the risk of the antique being worthless or priceless, so the contract can be voided.
买卖双方对一个古玩进行鉴定后以1000元交易，双方都不知道的是，鉴定师犯了一个错误，宝石其实价值100万。古玩的鉴定结果是双方的共同误解，送去鉴定表示双方并没有打算承担古玩一无所值或者价值连城的风险，合同可以撤销。
条款理解不同（Misunderstanding）Misunderstanding
Misunderstanding occurs when the parties attach materially different meanings to the contract terms. If neither party knows what the other is thinking, or if both parties know what the other is thinking, the contract is not formed at all due to a lack of mutual assent.
Misunderstanding是双方对合同条款的理解有实质性的不同（materially different meanings），如果双方都不知道对方心中所想，或者双方都知道对方心中所想，合同因为没有合意而根本没有形成。
Property management sells room "501". On the map, room 501 is on the 4th floor, but the buyer doesn't have a map and always thought the property management was selling a room on the 5th floor. Neither party knows what the other is thinking, so the contract is not formed due to a lack of mutual assent.
物业出售“501”号房，地图上501号房在4层，但买家没有地图，一直以为物业出售的是位于5楼的房屋。双方都不知道对方心中所想，合同因为没有合意而没有形成。
Property management sells room "501", but there is a dispute over whether the room is actually on the 4th or 5th floor. The property management knows the buyer wants to buy a 5th-floor room but deliberately does not clarify. The buyer knows the property management is selling a 4th-floor room but also plays dumb. Both parties know what the other is thinking, so the contract is not formed due to a lack of mutual assent.
物业出售“501”号房，但该房实际上位于4楼还是5楼有争议。物业知道买家想买5楼的房屋，故意不阐明。买家知道物业出售的是4楼的房屋，也故意装傻。双方都知道对方心中所想，合同因为没有合意而没有形成。
When a misunderstanding leads to a lack of mutual assent, either party can request that the contract be formed according to the other party's understanding.
当误解导致没有合意时，任何一方可以要求按照对方心中所想成立合同。
Property management sells room "501" on the 4th floor. The buyer thought the property management was selling a room on the 5th floor. After inspecting the 4th-floor room, the buyer is willing to purchase the 4th-floor room according to the property management's understanding of the terms, thus forming a transaction contract for the 4th-floor room.
物业出售位于4楼的“501”号房，买家以为物业出售的是位于5楼的房屋。买家考察4楼的房屋后，愿意按照物业对条款的理解购买位于4层的房屋，则成立4楼房屋的交易合同。
If only one party knows what the other is thinking, the contract is formed according to the other party's understanding.
如果只有一方知道对方心中所想，合同按照对方心中所想成立。
Property management sells room "501", which is on the 4th floor on the map. The property management knows the buyer wants to buy a 5th-floor room but deliberately does not clarify. However, the buyer genuinely believes the property management is selling a 5th-floor room. The contract is formed according to the buyer's understanding, meaning the property management is actually selling a room located on the 5th floor.
物业出售“501”号房，在地图上501号房在4层。物业知道买家想买5楼的房屋，故意不阐明。但买家真诚相信物业出售的是5楼的房屋。合同按照买家心中所想成立，即物业出售的实际上是位于5楼的房屋。
欺诈、虚假陈述、隐瞒Fraud, Misrepresentation, and Nondisclosure
If one party commits fraud, misrepresentation, or withholds a material fact, the other party can void the contract (voidable).
一方欺诈（fraud）、虚假陈述（misrepresentation）、隐瞒（withhold）重要事实（material fact），另外一方可以撤销合同（voidable）。
A chairman signs a large number of documents every day without ever reading them. One day, he signs a contract handed to him by his secretary to sell his house to the secretary at a very low price. The contract is voidable due to fraud.
董事长每天都要签署大量文件且从不过目，一天他签署了秘书递给他的将房屋以很低的价格卖给秘书的合同，合同因欺诈而可以撤销。
A weapons merchant says: "My spear is the best spear in the world." The weapons merchant did not make a misrepresentation; such rhetoric conforms to marketing practices.
兵器商人说：我的矛是世界上最好的矛。兵器商人不存在虚假陈述，类似的话术符合营销习惯。
A weapons merchant says: "My spear can pierce all shields in the world, and my shield cannot be pierced by any spear in the world." The weapons merchant has made a misrepresentation regarding at least one weapon.
兵器商人说：我的矛能刺穿世界上所有的盾，我的盾世界上所有的矛都刺不穿。兵器商人至少在一个兵器上存在虚假陈述。
A buys 10,000 shares of a company's stock from B for $5. B does not know that the company's industry may soon have a major development, and the stock price should be worth at least $10. A did not conceal a material fact; this transaction conforms to industry practices.
甲以5元的价格向乙购买10000股某公司股票，乙不知道的是该公司所在行业可能即将有重大发展，股票价格至少应当价值10元。甲没有隐瞒重要事实，该交易符合行业习惯。
A buys 10,000 shares of stock worth $10 a share from B for $5. A tells B: "$5 is the current market price." A committed fraud, and B can void the contract.
甲以5元的价格向乙购买10000股价值10元一股的股票，甲对乙说：5元是目前的市场价格。甲存在欺诈，乙可以撤销合同。
A is the chairman and largest shareholder of a company. A sells 10,000 shares of the company's stock to the market at $5 each. A does not disclose the material information that the company is insolvent and on the verge of bankruptcy. This is withholding material information. Those who bought the company's stock can sue to rescind the transaction.
甲是公司董事长和最大股东，以5元的价格向市场抛售10000股公司股票，甲没有披露公司已经资不抵债、即将破产的重大消息，这是刻意隐瞒（withhold material information），买了公司股票的人可以起诉撤销交易。
A patient sues a hospital for malpractice. The hospital's lawyer tells the patient that the hospital can pay a maximum of $100,000 in compensation, and the client accepts the settlement. In reality, the hospital's bottom line is $1,000,000. The settlement agreement is not voidable; such rhetoric is consistent with negotiation customs in settlements.
病人告医院执业过失。医院的律师对病人说，医院最多只能出10万赔偿，客户接受了和解。实际上医院的底线是100万。和解协议不可撤销，类似的话术符合和解中的谈判习惯。
A applies for a loan and subsequently loses his job. The bank approves the loan without knowing of A's unemployment. This is concealment of a material fact. A should have promptly notified the bank of his financial status. The bank can rescind the loan contract.
甲申请贷款后失业，银行在不知道甲失业的情况下批准了贷款，这是隐瞒重要事实。甲应当及时通知银行自己的经济状况。银行可以撤销贷款合同。
民事行为能力Capacity
Unlike China's phased definition of minors' contracts, in the United States, minors can void all contracts unless they ratify them upon reaching the age of majority.
和中国分阶段定义未成年人合同有所不同，美国未成年人可以撤销一切合同，除非在他成年时追认。
Most states define a minor as someone under 18 years of age and unmarried. Yes, many states allow individuals under 18 to marry.
大部分州对未成年人的定义是未满18周岁且未婚。是的，许多州允许不满18周岁的人结婚。
Furthermore, and also very different from China, we should never confuse minors with their parents. I will emphasize this again in the Torts chapter.
此外还和中国十分不同的是，我们永远不要把未成年人和家长混为一谈。在侵权章节我会再次强调。
A minor can disaffirm a contract made before turning 18 either before reaching the age of majority or shortly after. If it is a contract for the sale of goods, the minor must return the goods (even if used). If the goods have been consumed or if services were received, the provider of the services bears the loss.
未成年可以在他成年以前，或者成年后不久撤销18岁以前签订的合同。如果是物品买卖合同，未成年需要退回物品（用过的也可以）。如果物品已经被消耗，或者收到的是服务，由服务的提供方自行承担损失。
A 16-year-old student buys a game console. The store clerk calls the parents to ask how the experience is. The parent says, "I like it very much; I ratify the transaction on behalf of my child." The ratification is invalid; the student can still disaffirm the transaction.
16岁学生购买游戏机一台，店员打电话联系家长问游戏机体验怎样，家长说我很喜欢，我代表孩子追认交易。追认无效，学生仍然可以撤销交易。
For necessities (such as clothes and food) or necessary services (such as medical care), although the minor can disaffirm the contract, the merchant can claim reasonable compensation.
对生活的必需品（衣服、食物）或者必要的服务（医疗），未成年人虽然可以撤销合同，但商家可以主张合理报酬。
Please note that while the minor has the right to disaffirm the contract, the other party does not have this right.
请注意，未成年有权撤销合同，对方却并没有这个权利。
A 16-year-old student enters into a contract with a merchant to order a game console. The merchant refuses to ship the item, fearing the minor will disaffirm the contract. The minor can sue the merchant for breach of contract or demand specific performance to deliver the game console. Although the minor can choose to disaffirm the contract, if he does not, he still needs to pay the price according to the contract; therefore, the minor's promise to pay is valid consideration.
16岁学生和商家签订合同订购游戏机一台，商家担心未成年撤销合同所以拒绝发货。未成年人可以起诉违商家违约，或者要求强制交付游戏机。未成年人虽然可以选择撤销合同，但如果他不撤销合同，依然需要按照合同支付价款，所以未成年付款的承诺是有效对价。
Intoxication (or being under the influence of drugs, anesthesia, or medication) that leads to an inability to understand the meaning of the contract is another situation where a contract is voidable, but only if the other party had reason to know of the intoxication. Like minors, an intoxicated person can choose to ratify or disaffirm the contract when sober. If it involves necessities or necessary services, reasonable fees should be paid upon disaffirmance.
醉酒（或吸毒、麻醉、被药物影响，intoxicated）导致无法理解合同意思是另外一种可以撤销的情形，但只有对方有理由知道醉酒情形时才能作为撤销的事由。和未成年一样，醉酒的人清醒时可以选择追认或者撤销合同。如果是生活必须品或服务，撤销后应该支付合理费用。
Mental incapacity falls into two categories. One is intermittent; for contracts signed during an episode, the person can ratify or disaffirm them when lucid, or a guardian can ratify or disaffirm them after being appointed. Similar to minors, if it involves necessities or necessary services, reasonable fees should be paid upon disaffirmance.
精神疾病（mental incapacity）分两种，一种是间歇性的，那么在发病时签的合同，可以在清醒时追认或者撤销，或者可以在他被指定监护人后由监护人追认或撤销。和未成年同理，如果是生活必须品或必要的服务，撤销后应该支付合理费用。
The other category is when the mentally ill person has no lucid intervals and a guardian has complete control over them. In this case, the mentally ill person is similar to a person with "no civil capacity," and the contracts signed are void due to a lack of mutual assent.
另外一种是精神病人已经没有清醒的时候，监护人对精神病人有完全控制，这种情况精神病人类似于“无民事行为能力人”，签订的合同因没有合意而无效（void）。
胁迫Duress
A contract signed under physical duress is deemed to lack mutual assent and is void.
被武力胁迫（duress）而签订的合同视为没有合意而无效（void）。
A contract signed while A points a gun at B is void ab initio and is deemed non-existent.
甲用抢指着乙签订的合同自始无效，视为合同不存在。
Otherwise, if one party uses an improper threat to induce the other party to sign a contract, and the other party has no reasonable alternative, the contract is voidable by the victim.
除此之外，如果一方用不合理的威胁让另一方签订合同，而另一方没有合理的替代方案，受害方可以撤销合同（voidable）。
A urgently needs money. B offers $100,000 to buy A's antique, which is worth $200,000. There is no improper threat here, so it is not duress. Note that "taking advantage of someone's distress" is not a ground for voiding a contract.
甲急需用钱，乙提出10万买甲价值20万的古董，这并没有不合理的威胁，不是胁迫。注意“趁人之危”并不是合同可撤销的事由。
A urgently needs money. A's boss threatens that if A does not sell his antique for $100,000, he will fire A, making his situation even worse. The boss's demand can be considered duress.
甲急需用钱，甲的老板提出如果他不10万出售他的古董，就解雇他让他雪上加霜。老板的要求可以认为是胁迫。
不当影响Undue Influence
Undue influence is a contract arising from unfair persuasion. Specifically, this persuasion usually comes from a person who has dominance over or a special relationship with the victim. Because of this dominance or special relationship, the affected party is justified in assuming that the other party will consider their welfare or interests.
不当影响是基于不公平的说服行为产生的合同。具体来说，这种说服行为通常来自一个对受害方有支配权或特殊关系的人。由于这种支配地位或特殊关系，受影响的一方有理由认为对方会考虑到他的福利或利益。
A caregiver demands that the testator bequeath everything to her, or else she will quit. The testator, unwilling to change caregivers, has to agree to the caregiver's request. This is classic undue influence. In the Wills section (essay part), we will introduce special rules for wills made under undue influence; for such wills with unnatural results, proving the existence of undue influence does not require direct evidence.
保姆要求遗嘱人将遗嘱人全部遗赠给她，否则就辞职，遗嘱人不愿意换保姆，不得不同意了保姆的请求，这是经典的不当影响。在遗嘱篇（论文部分），我们会介绍因不当影响订立遗嘱的特殊规定，对于这种有不自然结果的遗嘱，证明不当影响的存在并不需要直接证据。
After her husband dies, a son constantly persuades his mother to sell him land at a fair price. The mother, overwhelmed by grief, is annoyed but eventually agrees to her son's request. "Repeated persuasion" may constitute undue influence, especially when there is a special relationship between the contracting parties. A "fair price" does not affect the voidability of the contract.
丈夫去世后，儿子不断劝说母亲将土地以公平的价格卖给他。母亲在悲痛中不厌其烦，但最终同意了儿子的要求。“重复地劝说”有可能构成不当影响，尤其是在合同双方有特殊关系的时候。“公平的价格”并不会影响合同的可撤销性。
If undue influence is exerted by a third party outside the contract, the victim can generally still void the contract. This is unless the other party to the contract did not know of the undue influence and has materially relied on the contract in good faith.
如果被合同以外的第三人施加不当影响，受害方原则上依然可以撤销合同。除非合同的另一方不知道不当影响的存在，且基于对合同的善意信赖已经作出安排。
违法/违反公序良俗Illegality / Contrary to Public Policy
Contracts made for illegal purposes or contrary to public policy are void. Examples include prostitution, purchasing drugs, hiring a hitman (murder), and violent interference with another's marriage.
为了违法（illegal）、违反公序良俗（contrary to public policy）而订立的合同无效（void）。比如嫖娼、购置毒品、买凶伤人（杀人）、暴力干涉他人婚姻等。
If the contract itself is not illegal but is used for an illegal purpose, and one party is unaware beforehand, the contract is not void. Even if aware, as long as:
如果合同本身并不违法，只是被用于非法目的，且一方事先并不知情合同并不会无效。哪怕知情，只要
They can still demand the other party perform the contract or seek damages for non-performance.
依然可以要求另一方履行合同，或者赔偿不履行合同带来的损害。
A and B negotiate to rent A's RV to B for manufacturing drugs, splitting the drug money. The contract is void ab initio.
甲乙协商将甲的房车租给乙用于制毒，毒资平分，合同自始无效。
A knows B will use his RV for unlicensed business activities but still rents it to B. A can void the contract or continue renting to B. If B breaches, A can even demand damages.
甲明知道乙要用自己的房车从事无证经营活动，依然租给了乙。甲可以撤销合同，也可以继续租给乙。如果乙违约，甲甚至可以要求损害赔偿。
不合情理Unconscionability
Common law emphasizes party autonomy and is reluctant to interfere with contracts merely because of a disparity in the substantive value of the consideration, as the essence of a transaction is that parties value items differently. This is quite different from "obvious unfairness" in Chinese law. Unless one party's consideration is merely nominal, such as buying land for $1, in which case we handle it using consideration theory rather than unconscionability.
普通法讲究意思自治，不太愿意仅仅因为双方对价的实质价值悬殊就干涉合同，因为交易的本质双方对物品价值的认识是不同的。这和中国法的“显失公平”有比较大的区别。除非一方的对价仅仅是象征性的，比如以1元的价格购买土地，这种情况我们用对价理论来处理，而非不合情理。
Unconscionability refers to a situation where the victim lacks bargaining power, and the other party uses this to insert terms into the contract that are favorable to them but unfair. Examples include confession of judgment clauses upon breach, disclaimer of warranty clauses, unreasonable terms hidden in contracts of adhesion for necessities where the buyer has no choice, and exculpatory clauses releasing liability in advance.
不合情理（unconscionability）是指受害方没有协商筹码（bargaining power），而另一方借此在合同中加入对自己有利但不公平的条款。比如一旦违约就自愿承认败诉判决的条款（confession of judgment clauses），商家免除质保的条款（disclaimer of warranty），不合理的条款被写在必需品的格式合同里而买家别无选择（contracts of adhesion），提前免除责任的条款（exculpatory clauses）。
Although these terms are usually found in standard form contracts drafted by merchants, we should not confuse them with "standard contracts" in the Chinese Civil Code. In the Civil Code, "standard contracts" are invalid because sufficient notice was not given, so highlighting terms unfavorable to the non-drafting party or giving sufficient notice is enough. But the unconscionability we learn here has nothing to do with whether the weaker party received notice; the focus is that the victim had no choice but to accept these unreasonable terms. Conversely, if there was bargaining power and the parties carefully crafted and communicated the terms, and one party still accepted them, it does not constitute unconscionability.
虽然这些条款通常在商家起草的格式合同中，但我们不要和中国民法典的“格式合同”混淆，民法典“格式合同”无效是因为没有给出足够的提示，所以只要高亮对非起草方不利的条款或者作出足够的提示即可。但我们这里学的不合情理和弱势一方是否得到通知无关，重点是受害方除了接受这些不合理的条款别无选择。反之，如果明明有协商筹码，双方对合同的条款精雕细琢、仔细沟通，一方依然接受了这些条款，也不属于不合情理的情况。
At an auto show, a seller offers a display car with a $5,000 discount but no warranty. After careful consideration, the buyer still chooses this car without a warranty. This is not unconscionable.
在车展上，卖家提供一个展示用车，虽然优惠5000美元，但没有保修。买家仔细斟酌后，依然选择了这个没有保修的车，并非不合情理。
When dealing with unconscionable contracts, courts usually will not enforce the terms unfavorable to the victim (unenforceable). If these terms can be severed from the contract, the rest of the contract can still be enforced.
处理不合情理的合同，法院通常不会执行对受害方不利的条款（unenforceable）。如果这些条款能够从合同中剥离，合同的其他部分依然可以执行。
We summarize the situations of defective contracts as follows:
我们把合同瑕疵的几种情况总结如下：
| Situation | Result |
|---|---|
| Misunderstanding | No contract, no mutual assent |
| Direct physical duress | No contract, no mutual assent |
| Direct purpose is illegal or violates public policy | No contract, no mutual assent |
| Contract signed by a mentally ill person under guardianship | No contract, no mutual assent |
| No consideration, illusory consideration | No contract, no mutual assent |
| Violation of the Statute of Frauds | Unenforceable |
| Unconscionability | Unenforceable |
| Mutual mistake | Voidable |
| Fraud, misrepresentation, concealment of material facts | Voidable |
| Contract signed by a minor | Voidable |
| Intoxicated (alcohol/drugs), and the other party knows or has reason to know | Voidable |
| Contract signed during an episode of intermittent mental illness | Voidable |
| Improper threat other than direct physical duress | Voidable |
| Undue influence | Voidable |
| Contract itself is not illegal, but used for an illegal purpose | Voidable |
| 情形 | 结果 |
|---|---|
| 条款理解不同（misunderstanding） | 没有合同、没有合意 |
| 直接武力胁迫 | 没有合同、没有合意 |
| 以违法、违反公序良俗为直接目的 | 没有合同、没有合意 |
| 被监护人接管的精神病人签订的合同 | 没有合同、没有合意 |
| 没有对价、虚无的对价 | 没有合同、没有合意 |
| 违反反欺诈法 | 无法执行（unenforceable） |
| 不合情理（unconscionable） | 无法执行（unenforceable） |
| 共同误解（mutual mistake） | 可撤销 （voidable） |
| 欺诈、虚假陈述、隐瞒重要事实 | 可撤销 （voidable） |
| 未成年签订的合同 | 可撤销 （voidable） |
| 被酒精（药物）影响，对方明知或应知 | 可撤销 （voidable） |
| 间歇性精神病发作期间签订的合同 | 可撤销 （voidable） |
| 非直接武力胁迫以外的不当威胁 | 可撤销 （voidable） |
| 不当影响（undue influence） | 可撤销 （voidable） |
| 合同本身不违法，但被用作违法意图 | 可撤销 （voidable） |
合同的修改Modification of Contracts
普通法下合同的修改Modification of Contracts under Common Law
Under common law, modifying a contract requires new consideration, similar to the "pre-existing legal duty" rule discussed earlier.
普通法下修改合同需要新的对价，类似于前文的“已有法律义务”。
A owes B $500, but A is about to go bankrupt, so A offers to not file for bankruptcy in exchange for only having to repay $200, and B agrees. Consideration does not have to be an affirmative act; it can also be a forbearance. "Not filing for bankruptcy" is valid consideration. After A repays the $200, even if his financial situation improves, B cannot demand the remaining amount.
甲欠乙500美元，但甲即将破产，于是用不申请破产换取只用偿还200美元，乙同意。对价不必是积极的行为，也可以是消极的忍受，“不申请破产”是有效的对价。当甲偿还完200美元后，即使他的资金状况好转，乙也不可以再要求剩下的金额。
UCC下合同的修改Modification of Contracts under the UCC
As also mentioned earlier, modifying a contract under the UCC does not require new consideration, but a modification without consideration must be made in good faith, usually due to objective reasons.
也如前文所述，UCC下修改合同不需要新的对价，但没有对价的修改需要基于善意（good faith），通常是客观原因。
合同的解释Interpretation of Contracts
口头证据规则Parol Evidence Rule
原则General Rule
The parol evidence rule states that a contract should be governed by its written terms; oral or written communications made prior to signing cannot be used if they contradict the text of the formal written contract.
口头证据规则（parol evidence rule）说的是合同应当以书面为准，签约之前的口头或书面沟通如果和正式的书面合同原文相抵触则无法使用。
"Cannot be used" means that the jury will not have access to this evidence. Although we have not yet studied civil procedure in depth, you can first understand this basic principle: generally, the judge decides questions of law, while questions of fact are left to the jury. Since the jury will not be exposed to prior evidence that contradicts the contract, they will only decide based on the text of the contract.
“无法使用”的意思是陪审团无法接触到这些证据。虽然我们还没有深入学习诉讼法，但可以先了解这个基本原则：通常来说，法官只审理法律问题，事实问题交给陪审团。既然陪审团都接触不到先前与合同相抵触的证据，那只会按照合同的原文来裁决。
Note the spelling difference from "parole". However, do not let the name of the parol evidence rule cause you to overlook that written communications prior to signing are equally subject to the parol evidence rule.
注意单词的拼写和假释（parole）有区别。但不要因为口头证据规则的名字就忽略了签约之前的书面沟通同样受口头证据规则约束。
A and B sign a sales contract with a unit price of $5. In court, A testifies that the unit price orally agreed upon by both parties before signing was actually $6. This testimony cannot be used; if tried by a jury, the jury should not be exposed to this testimony.
甲乙签订单价5元的买卖合约，法庭上甲作证说双方签约前口头约定的单价其实为6元。该证词无法使用，如果由陪审团审判，陪审团不应该接触这个证词。
If the prior parol evidence does not contradict the text of the written contract but merely supplements it, we must look at whether the contract is completely/fully integrated. If the contract is only partially integrated, it can be supplemented. For a completely integrated contract, no prior oral or written evidence can be used to add any terms.
如果签约之前的口头证据不和书面合同原文抵触，只是进行补充，我们要看合同是否完备（completely/fully integrated），如果合同并不完备（partial integration），则可以进行补充。对于一个完备的合同，不能用之前的口头或书面证据增加任何内容。
Usually, the fact pattern will indicate whether the contract contains a merger clause.
通常题目会交代合同中是否有完备条款（merger clause）。
A merger clause typically looks like this:
Merger clause通常长这样：
Merger. This Agreement constitutes the final, exclusive agreement between the parties on the matters contained in this Agreement. All earlier and contemporaneous negotiations and agreements between the parties on the matters contained in this Agreement are expressly merged into and superseded by this Agreement.
Merger. This Agreement constitutes the final, exclusive agreement between the parties on the matters contained in this Agreement. All earlier and contemporaneous negotiations and agreements between the parties on the matters contained in this Agreement are expressly merged into and superseded by this Agreement.
If there is none, the UCC presumes that the contract is partially integrated, and the default position on the MBE is also partial integration. Occasionally, a question will ask why a contract without a merger clause is still completely integrated (on certain issues), and we can consider:
如果没有，UCC预设合同是不完备的，MBE的默认观点也是不完备的。偶尔会问一个为什么没有merger clause的合同（在某些问题上）依然是完备的，我们可以考虑：
Essay questions, in particular, should discuss these two points.
论文题尤其应该讨论这两点。
After the contract is formed, the seller claims that the buyer can only purchase the goods from them for the next 5 years (an exclusivity agreement). It is highly unreasonable that such an important term does not explicitly appear in the contract. The contract should be considered completely integrated on this point; even if the contract lacks an explicit merger clause, evidence proving the agreement is exclusive should not be introduced.
合同成立后卖家主张买家未来5年只能从自己这里采购该商品（独家协议），这样的重要条款居然没有明文出现在合同中是非常离谱的。应当认为合同在这一点上是完备的，即使合同没有明文的合并条款，也不应该引入证明协议是独家的证据。
例外Exceptions
Parol evidence after signing falls outside the scope of this rule and can generally be used. Under common law, a "no-oral-modification" (NOM) clause is invalid, but pay attention to the requirement of consideration.
签约后的口头证据不属于该规则的范围，通常可以使用。普通法下，“合同不可以口头修改”的条款（no-oral-modification clause, NOM clause）是无效的，但要注意对价的要求。
A signs a race car driver for one year of service for $1 million, and they orally agree to change it to $1.2 million a year. The contract modification lacks consideration, so it is unenforceable.
甲以100万签约赛车手服务一年，口头约定改为120万一年。合同的修改没有对价，所以无法执行。
Under the UCC, NOM clauses are valid by default. If a non-merchant is involved in the transaction, the non-merchant must separately sign the NOM clause on a form supplied by the merchant. However, the UCC also provides that if the contract is orally modified anyway, it can operate as a waiver of the NOM clause by both parties, even if it also violates the Statute of Frauds.
UCC下，NOM条款默认是有效的。如果交易双方有非商家，那需要非商家对商家提供的表格上的NOM条款单独签名。但是，UCC又规定，如果无论如何合同还是被口头修改了，可以视为双方对NOM条款的豁免，哪怕同时也违反了反欺诈法。
In practice, there is significant controversy over whether an oral modification of a UCC contract is always treated as a waiver. The prevailing view is that if it can always be treated as a waiver, the UCC provision making NOM clauses valid by default would be meaningless. Therefore, an oral modification is only effective if at least one party has materially changed their position in reliance on the oral modification. Alternatively, whether the parties intended to waive the clause should be left to the jury as a question of fact.
实务上对UCC合同口头修改的行为是否一律视为豁免争议很大。主流观点认为，如果一律可以视为豁免，UCC关于NOM条款默认有效的规定就毫无意义，所以至少要在一方基于口头修改的信赖作出安排时，口头修改才有效。或者，双方是否有豁免的意思表示要作为一个事实问题让陪审团决定。
UWorld takes the position that if the parties agree to modify the delivery date, performing according to the modified contract is itself a change of position. Under this view, as long as there is reliance such as performance, both common law and UCC contracts can be orally modified, regardless of how strongly the contract itself emphasizes that oral modifications are prohibited. So far, the released past questions from the NCBE all reflect this view.
UWORLD认为，如果约定修改交付日期，按照修改后的合同履行本身就是一种安排。在这种观点下，只要有履行等信赖行为，无论是普通法还是UCC合同都可以被口头修改，无论合同本身如何强调不可以口头修改。到目前为止，NCBE放出的真题都是这个观点。
Kaplan, on the other hand, believes that merely agreeing to a price increase does not constitute a detrimental change of position by the seller; thus, under a valid NOM clause, an oral modification of the price would be invalid.
Kaplan则认为，仅仅约定涨价，卖方不算是作出了有损害的安排，那在有效的NOM条款下，口头修改价格就是无效的。
The UCC also specifically provides that if one party has not yet materially changed their position and the other party reneges, the latter can retract the waiver of the NOM clause, which is deemed a retraction of the oral modification.
UCC还单独规定，如果一方还没有作出安排，另外一方反悔，可以撤回对NOM条款的豁免，也就视为撤回了口头修改。
In addition to evidence subsequent to the signing of the contract not being bound by the parol evidence rule, exceptions to the parol evidence rule are also frequently tested.
除了合同签约之后的证据不被口头证据规则约束，口头证据规则的例外也是常考的内容。
A and B sign a sales contract with a unit price of $5. In court, A testifies that the unit price orally agreed upon by both parties before signing was actually $5,000, and a clerk accidentally omitted the word "thousand". This testimony is helpful for the reformation of the contract and can be introduced.
甲乙签订单价5元的买卖合约，法庭上甲作证说双方签约前口头约定的单价其实为5000元，职员不小心漏了一个thousand。该证词对合同的重写有帮助，可以引入。
It does not necessarily require such an outrageous mistake to reform a contract. In the latest 200 questions released by the NCBE, both parties omitted an addendum regarding a price increase. The answer indicated that this addendum could be introduced by reforming the contract, unconstrained by the parol evidence rule.
并非一定要如此离谱的误解才能重写合同，在NCBE放出的最新200个题中，双方都遗漏了一份加价的附录，答案认为可以通过重写合同引入这封附录，不受口头证据约束。
A and B signed a car purchase contract and orally agreed that the contract would only become effective if A obtained sufficient financing. This oral agreement can be introduced.
甲乙签订购车合同并口头约定只有甲获得足够的贷款时合同才会生效，口头约定可以引入。
Although not included in the car purchase contract, the buyer can introduce an oral promise that each maintenance service will only cost $10, because it is a collateral agreement relatively independent of the main contract. It should be noted that the parol evidence rule dictates that the jury should not be exposed to pre-contractual evidence at all; therefore, its exception merely means that the testimony is admissible, not that the jury must necessarily believe the seller promised $10 per maintenance.
虽然购车合同中没有，但是买家可以引入保养每次只需要10美金的条款的口头承诺，因为它是一个和主合同相对独立的附属条款。要注意的是，口头证据规则是陪审团压根不应该接触签订合同之前的证据，那么它的例外也仅仅是说该证词可以被引入，并非陪审团就一定要相信卖家承诺了每次保养只需要10美金。
解释合同的规则Rules of Contract Interpretation
文意原则Plain Meaning Rule
Courts interpret contracts using their ordinary, plain meaning, unless it is obvious that another meaning should be applied.
法院用字面通常的意思解释合同，除非明显应该用其他意思来解释。
In legal documents, "leave" usually means permission, which is rarely used this way outside of legal contexts. Courts will not interpret "leave" as permission in other contexts, nor will they interpret "leave" as departing when applying for permission.
法律文书中leave通常是许可的意思，法律文书以外的地方几乎不这么用。法院不会在其他地方把leave解释为许可，也不会在申请许可的时候把leave解释为离开。
冲突解释Interpretation of Conflicting Terms
When there is a conflict between different terms, handwritten or typed terms prevail over printed terms, and words prevail over numbers.
不同条款之间冲突时，手写或者用打字机打（typed）的条款要优先于用打印机打（printed）的条款，单词要优先于数字。
A and B signed a contract stating the price as three thousand dollars ($4000). The contract price should be $3,000.
甲乙签订合同约定价格为three thousand dollars ($4000)。合同价格应为3000元。
履约习惯、交易习惯、行业惯例Course of Performance, Course of Dealing, and Trade Usage
When a contract is ambiguous or silent on an issue, we can use course of performance, course of dealing, and trade usage to interpret the contract.
合同有歧义或没有规定的时候，我们可以用履约习惯（course of performance）、交易习惯（course of dealing）、行业惯例（trade usage）来解释合同。
In specific applications, course of performance prevails over course of dealing, and both course of performance and course of dealing prevail over trade usage.
具体适用的时候，履约习惯优先交易习惯，履约习惯和交易习惯又优先行业惯例。
A contract for 12 installments of delivery does not specify who bears the sales tax, but the delivery notes for the first 9 months all show that the merchant covers the tax. This is a course of performance.
12期送货的合同没有约定消费税的承担，但是前9个月每次送货单都显示商家包税。这是履约习惯。
The contract does not specify who bears the sales tax, but in all previous transactions between the parties, the merchant covered the tax. This is a course of dealing.
合同没有约定消费税的承担，但是双方此前每次交易都是商家包税。这是交易习惯。
The contract does not specify who bears the sales tax. Although the trade usage is for the buyer to pay the tax, in all previous transactions between the parties, the merchant covered the tax. Therefore, the merchant should cover the tax this time, as course of dealing prevails over trade usage.
合同没有约定消费税的承担，虽然行业惯例是买家付税，但是双方此前每次交易都是商家包税。所以本次应该商家包税，这是交易习惯优先于行业惯例。
Please note, however, that if the contract has an explicit provision, the contract provision should govern, and these courses or usages should not be applied.
但请注意，如果合同有明确规定，应该以合同规定为准，不应该适用这些习惯。
The contract stipulates that the buyer bears the sales tax. Even though the merchant covered the tax in the previous deliveries, in all prior transactions, and under trade usage, the merchant can still require the buyer to bear the tax for this delivery, and the merchant can also claim that the buyer should pay off the taxes for the previous deliveries.
合同约定消费税由买家承担，虽然前几次送货都是商家包税，此前每次交易也商家包税，行业惯例也是商家包税，但本次送货依然可以要求买家承担税费，商家也可以主张买家应当付清前几次的税费。
The UCC further provides that evidence of these three courses (or usages) can be used to supplement and interpret a contract without being barred by the parol evidence rule, even if the contract is completely integrated.
UCC进一步认为，这三种习惯（惯例）证据可以用来补充和解释一个合同而不受口头证据限制，即使合同是完备的。
Even if the contract price is very clear and it is noted that the contract is completely integrated, the buyer can still introduce a course of dealing where they received a 5% discount every time previously, to argue that they should also receive a 5% discount for this transaction. When answering questions, consider discounts and prices as two non-conflicting systems; a clear price does not mean there is no discount.
即使合同的价格非常明确，也注明了合同是完备的，买家依然可以引入此前每次都享受5%折扣的交易习惯，主张本次交易同样享受5%的折扣。做题时认为折扣和价格是不冲突的两个体系，价格明确不意味着没有折扣。
对起草方不利的原则Contra Proferentem (Interpretation Against the Drafter)
When a contract is ambiguous, the principle is to interpret it against the drafter. However, when there is a course of performance, course of dealing, or trade usage, we consider the contract to be unambiguous.
合同有歧义（ambiguous）时，以对起草方不利的解释为原则。但是，当有履约习惯、交易习惯、行业惯例存在时，我们认为合同是没有歧义的（unambiguous）。
Even if the contract is unambiguous, when the contract terms differ from a party's reasonable expectations, the court may forcibly interpret it against the drafter. This method of interpretation is typically used for adhesion contracts.
即使合同没有歧义，但合同条款和一方的合理期待不同时，法院也可以强行以对起草方不利的方式解释。这种解释方法通常用于格式合同。
To review, whether the parties want to introduce evidence of who drafted the contract, or evidence of course of performance, course of dealing, or trade usage, neither is restricted by the parol evidence rule. This is because such evidence is used to interpret the contract, rather than to introduce conflicting terms or add new terms to the contract.
复习一下，无论是双方要引入谁起草合同的证据，还是履约习惯、交易习惯、行业惯例的证据，都不受口头证据规则的限制，因为这是在解释合同，而不是引入与合同冲突的条款或增加合同条款。
UCC对解释合同的规定UCC Rules on Contract Interpretation
UCC对合同空白的补充UCC Gap Filling
We mentioned earlier that the UCC only requires a contract to state the quantity, and other terms can be supplied by UCC provisions (gap filling). We also mentioned that describing the quantity as "all the parts I require" or "all the parts you produce" is acceptable under the UCC.
我们之前提到，UCC只要求合同有数量即可，其他方面都可以通过UCC的规定来补足合同（gap filling）。我们还提到过，用“我需要的所有零件”，“你生产的所有零件”描述数量是UCC可以接受的。
As a review, an agreement to "purchase any quantity of parts specified by the buyer at a price of $5 each" does not constitute a contract. First, it lacks the key element of a contract for the sale of goods: quantity. Most importantly, the buyer has not provided any consideration; if he specifies a quantity of zero, he suffers no detriment. Although it cannot be deemed a contract, it should be treated as an offer. As long as the seller has not revoked the offer, the buyer's act of specifying the quantity should be deemed an acceptance, and the contract is formed at the time of specification.
复习一下，约定“以5元一个的价格，采购买家指定的任何数量的零件”是没有合同的。首先，这里缺乏了物品买卖合同的关键要素：数量。最重要的是，这里买方没有提供任何对价，如果他指定数量为0，就没有任何损失。虽然不能视为合同，但应当视为要约，卖家只要没有撤回约定，买家指定数量的行为应当视为接受要约（acceptance），合同在指定之时起成立。
Now let's learn how the UCC fills in the important elements of a contract. It is not hard to remember if we apply a little common sense.
现在我们来学习UCC如何补足合同中的重要元素，我们稍微结合常理就不难记住。
We may often see news about going to the emergency room in the US and receiving an astronomical bill after returning home, which contrasts with China's "pay first, treat later" approach (though major domestic hospitals are changing now). "Provide services first, send the bill later, and the client pays according to the bill" is a long-standing Western trade custom. If an exam question states that the seller will not ship the goods if the buyer does not pay, this is also correct, because the UCC does not prescribe a strict sequence. However, if an option implies that the buyer pays within a reasonable time after receiving the goods, it is incorrect, because the UCC rule is essentially "cash on delivery" (payment upon receipt).
我们或许总是看到在美国去趟急诊室，回家之后收到天价账单的新闻，和中国“先交费、再治病”形成对比（现在国内大医院也有所改变）。“先提供服务，再发账单，甲方按照账单付款”是西方长久以来的交易习惯。如果考题中出现买家不付款，卖家就不发货，也是正确的，因为UCC并没有规定谁先谁后。但如果选项中暗示你买家在收到货物后合理时间内付款，则是错误的，因为UCC的规定是“一手交钱，一手交货”。
A and B agree to trade a new car, without agreeing on any other terms. Trying to fill in the other elements using the UCC: the price could be the official reference price, the time of delivery should be within a few weeks (which can be delayed under special circumstances), the place of delivery is the seller's place of business or residence, the time of payment is when the seller delivers the car, and if the buyer does not choose the model and color of the car, the seller may make the selection on their behalf.
甲乙双方约定交易新车一辆，双方没有约定其他条款。用UCC尝试补足其他元素：价格可以用官方参考价，交易时间应当在数周内（如果有特殊情况可以延迟），送货地点是卖家营业地址或家中，付款时间是卖家交付车时，如果买家不选择车的型号和颜色，卖家可以代为选择。
隐含质保Implied Warranties
The UCC provides that even if not explicitly stated in the contract, contracts for the sale of goods implicitly include the following warranties of quality, known as implied warranties.
UCC规定，即便合同中没有注明，买卖合同都隐含了如下质量保证，这叫做隐含质保（implied warranty）。
The warranty of title applies to any seller. If there is a defect in the property rights of the goods (ownership, security interests, etc.), the seller shall be held liable, which is easy to understand. Note that if the buyer chooses to purchase despite knowing of the defect, they can no longer assert the warranty of title.
所有权保证（warranty of title）适用任何卖家，如果商品的物权（所有权、抵押权等）有瑕疵，卖家应当负责任，这很好理解。注意如果买家明知道有瑕疵依然选择购买，则不可再主张物权保证。
The implied warranty of merchantability is perhaps more accurately described as a "usability" warranty, meaning that the goods must at least be fit for the ordinary purposes for which such goods are used. However, only merchants are required to warrant merchantability; ordinary persons are not.
适售性保证（warranty of merchantability），其实更确切地说是“可用性”保证，就是至少商品要能够在它正常的范围内使用。但只有商家需要保证适售性，一般人不需要保证。
Apple sells a used car to Microsoft. Although Apple is a merchant of mobile phones, it is not a merchant of used cars, so it does not need to warrant that the car sold to Microsoft can be used normally.
苹果把一台二手车卖给了微软，苹果虽然是手机商，但不是二手车商，不用保证卖给微软的车可以正常使用。
The warranty against infringement also applies only to merchants, requiring a warranty that the goods are free of any patent, copyright, trademark, or other infringement claims. However, if the buyer is sued by a claimant, the buyer must promptly notify the seller and give the seller an opportunity to defend the suit; otherwise, the buyer is deemed to have waived the right to assert a claim against the seller.
侵权保证（warranty against infringement）也只适用于商家，要求保证商品没有任何专利、版权、商标等问题。但如果买家被主张权利的人起诉，买家必须及时通知卖家并让卖家有机会参加诉讼，否则买家视为放弃向卖家主张权利。
The implied warranty of fitness for a particular purpose arises when the seller knows the buyer is purchasing the goods for a specific purpose, yet provides goods that do not meet the buyer's specific purpose.
可以用于特定用途的保证（warranty of fitness for a particular purpose），卖方知悉买方购买商品需要用于特定意图，依然提供了不符合买方特定意图的商品。
Apple sells a non-waterproof phone to Gates. Gates plays with the phone while swimming, causing water damage. The ordinary purpose of a phone does not involve contact with water, so Apple is not liable.
苹果把不防水的手机卖给了盖茨，盖茨一边游泳一边玩手机导致进水损坏。手机的一般用途不会与水接触，苹果不需要承担责任。
Gates tells Apple that he needs to play with the phone while swimming, and Apple sells him a phone. A good waterproof phone can usually be submerged in 1.5 meters of water for 30 minutes, but Gates's phone is damaged as soon as he enters the water. Apple is liable.
盖茨跟苹果说自己需要在游泳的时候玩手机，苹果销售了一台手机。一台好的防水手机通常能在1.5米水深浸泡30分钟，但盖茨刚下水手机就损坏了，苹果需要承担责任。
表意质保Express Warranties
The seller's statements about the goods, descriptions on the packaging, statements in promotional advertisements, and samples displayed in the store all constitute express warranties. If the goods do not conform to the actual promises, the seller is liable. What we need to remember is the exception: mere sales puffery and embellishments do not constitute a commitment to the quality of the goods.
卖家对商品的陈述、包装上的叙述、宣传广告的叙述、在卖场展示的样品，都构成表意质保（express warranty）。如果商品和实际承诺的不符，卖家需要承担责任。我们需要记的是例外：单纯的营销话术和美化效果并不构成对商品质量的承诺。
Telling a customer, "You will be the most beautiful person in the world wearing this dress," is merely general sales puffery. If the customer buys it, wears it, and feels she is not the most beautiful person in the world, she cannot assert a warranty claim.
对顾客说“穿上这件衣服你就是全世界最美的人”，这只是一般的行销话术，如果顾客买回家穿上之后觉得并不是全世界最美的人，也不可以主张质保。
A burger vendor's advertisement uses techniques to photograph the burger as round and plump, but in reality, the burger is not that round and plump. This typically does not constitute a commitment to the quality of the goods.
汉堡商的广告用技巧把汉堡拍得圆润饱满，但实际上汉堡并没有那么圆润饱满，通常不构成对商品质量的承诺。
保险和风险转移Insurable Interest and Risk of Loss
Unless otherwise agreed in the contract, a buyer's insurable interest arises when the goods can be reasonably identified.
除非合同另有约定，买家可保险的利益从货物能够被合理地确定时产生。
A buyer purchases a rare used car and insures it. That night, the used car is accidentally destroyed by fire. The buyer can claim compensation from the insurance company.
买家购买一辆稀有的二手车并投保。当晚，该二手车被意外烧毁，买家可以向保险公司主张赔付。
Two buyers each purchase an identical part from a seller and insure it. That night, the only two parts left in the seller's warehouse are accidentally destroyed by fire. The buyers cannot claim compensation from the insurance companies. Of course, because the goods were not delivered, the buyers do not have to pay.
两个买家分别找卖家买了两个一样的零件并投保。当晚，卖家仓库里有10个一样的零件，尚未为买家贴标签或分离，仓库发生火灾导致零件被意外烧毁。由于货物尚未特定化，买家无法向保险公司主张赔付。当然，因为货物没有交付，买家也不必付款。
Ten buyers each purchase an identical part from a seller and insure it. The seller happens to have exactly 10 parts in the warehouse and attaches a shipping label to each part according to the buyers' addresses. That night, 9 parts are accidentally destroyed by fire. Because they have all been labeled, the insurance companies should compensate the respective buyers based on the addresses. The remaining unburned part should be delivered to the buyer named on its shipping label.
10个买家分别找卖家买了10个一样的零件并投保，卖家仓库里刚好有10个零件，并根据买家的地址给每个零件贴上了快递标签。当晚，9个零件被意外烧毁，因为都已经被贴上了标签，保险公司应当按照买家的地址分别赔付。剩下一个未烧毁的零件应当交付给快递标签上的买家。
Risk of loss refers to the process by which the risk of damage to or loss of the goods transfers from the seller to the buyer. If there is an agreement, the agreement prevails; if there is no agreement, the risk of loss transfers upon delivery of the goods.
风险转移是指货物损毁、灭失的风险从卖家转移到买家的过程。有约定的以约定为准。在没有约定且不涉及承运人的情况下（UCC § 2-509(3)），如果卖家是商人（merchant），风险在买家实际收到货物（receipt）时转移；如果卖家不是商人，风险在卖家提供交货（tender of delivery）时转移。
In cases involving logistics, we sometimes encounter the FOB term heard in International Economic Law, but the usage of the FOB term in North America is slightly different from what is learned in International Economic Law.
在涉及物流的案件中，我们有时候会碰到三国法中听过的FOB术语，但北美的FOB术语用法和三国法中学到的略有不同。
For goods shipped from New York to Los Angeles, we use "FOB New York" to indicate that the risk of loss transfers upon delivery to the carrier (shipment contract), and "FOB Los Angeles" to indicate that the risk of loss transfers upon arrival at the destination (or another location specified by the buyer) (destination contract).
货物从纽约运到洛杉矶，我们用FOB New York表示交付承运时风险转移（shipment contract），用FOB Los Angeles表示运到目的地（或其他买家指定的地点）时风险转移（destination contract）。
If not specifically stated, the contract defaults to transferring the risk of loss upon delivery into the hands of the carrier (i.e., a shipment contract).
如果没有特别注明，合同默认交付到物流手中完成风险转移。
A buyer purchases 10,000 parts without insurance. The night after the seller delivers them to the carrier, all the parts are accidentally destroyed. The buyer still has the obligation to pay.
买家购买10000个零件，没有投保。卖家交付承运人后当晚零件全部被意外损毁，买家依然有付款义务。
合同的履行Performance of Contracts
普通法合同的履行Performance of Common Law Contracts
Under common law, if a party's performance is defective, as long as there is "substantial performance," the other party still has a duty to perform. Of course, the other party can claim damages for the defective performance. However, if a party fails to render substantial performance, the other party may refuse to pay.
在普通法下，如果一方的履行有瑕疵，只要“实质性履行”（substantial performance），对方就仍然有履行义务。当然，对方可以就履行的瑕疵要求损害赔偿。但如果一方无法构成实质性履行，则对方可以拒绝付款。
A and B agree to build a sports stadium, and B completes it one week late. Under common law, if the contract does not specify that "time is of the essence," a minor delay by default does not constitute a failure of substantial performance. A still has a duty to pay, but can claim damages caused by the delay, such as a reasonable week's rent. The damages must be foreseeable at the time of contracting, as referenced in the later section on damages.
甲和乙约定修建一个体育场馆，乙延期一周完工。在普通法下，如果合同没有注明履行时间是关键因素（time is of the essence），则默认不严重的延期不构成违反实质性履行。甲依然有付款义务，但可以主张延期造成的损失，比如一周的合理租金。损失要可以在签订合同时预见，参考后文赔偿金的部分。
A and B agree to build a sports stadium to be used for the Olympic opening ceremony. B fails to complete it before the opening ceremony. Time is clearly of the essence in this contract, and A has no duty to pay.
甲和乙约定修建一个体育场馆，约定作为奥运会开幕式场馆使用。乙没有在奥运会开幕式前完工。该份合同中时间明显是关键因素，甲没有付款义务。
Exam questions will not make candidates overly struggle with whether there is substantial performance; they usually provide clear signals. For example, using pipes of a different brand than specified in the contract but with similar functions constitutes substantial performance. If it fails to even constitute substantial performance, the question will tell you that there is a material deviation from the purpose of the contract, or the function is completely unusable, etc.
题目中不会让考生在是否实质性履行中过度纠结，通常会给明显的信号。比如没有选用合同中约定的品牌但功能类似的管道就属于实质性履行。如果连实质性履行都无法构成，题目会告诉你和合同的目的有重大出入，或者功能完全无法使用等。
We need to note the difference between the common law "substantial performance" rule and the UCC "perfect tender" rule.
我们需要注意的是普通法“实质履行”规则和UCC下“完美交货”规则的区别。
UCC下合同的履行Performance of Contracts under the UCC
Performance of contracts under the UCC applies the "perfect tender" rule. That is, the goods delivered must conform exactly to the contract description. The seller cannot claim to have "substantially performed" the contract; for example, substituting blue parts for red parts, even if the functions are very similar, constitutes a breach. The buyer may choose to accept, reject, or accept part of the goods, and under any of these choices, may claim that the seller is in breach.
UCC中合同的履行适用“完美交货”（perfect tender）规则。即必须交付与合同描述完全一致的货物。卖家不能主张“实质性履行”了合同，比如用蓝色零件替代红色零件，即使功能十分类似，也构成违约。买家可以选择接受、退回或者接受部分货物，而且在任何一种选择下，都可以主张卖家违约。
If the buyer rejects the goods, they can claim non-payment and the return of any prepaid deposit. However, the buyer must:
买家如果拒绝货物，可以主张不付款并退回预付的任何定金。但买家必须：
If the time for delivery has not yet expired and the seller has delivered non-conforming goods, the seller has the opportunity to cure before the delivery deadline.
如果收货时间没有到，卖家又寄送了不符合要求的货物，卖家有机会在送货时间截止之前补救。
可分割的合同、分期合同Divisible Contracts and Installment Contracts
However, for divisible contracts and installment contracts, the rules under common law and the UCC are similar: as long as the breached part does not substantially impair the whole, we generally allow the contract to be treated separately.
但对于可分割的合同、分期合同，普通法和UCC的规定是类似的，即只要违约的部分不实质性影响整体部分，原则上我们允许把合同分开处理。
A agrees that B will come to A's house to teach every Wednesday for a year. An absence of one week will not substantially impair the contract; A can deduct the tuition for that week or the damages caused by the absence, but cannot claim that B committed a material breach.
甲约定乙每周三来家里上课，为期一年。缺勤一周并不会实质性影响合同，甲可以扣除这一周的课时费或者这一周没来上课造成的损失，但不能主张乙根本违约。
A agrees that B will deliver 100 pounds of rice every Wednesday for a year. B's failure to deliver or delivery of non-conforming goods on a particular Wednesday will not substantially impair the entire contract; A can claim damages for the non-delivery that week, but cannot claim that B committed a material breach.
甲约定乙每周三送货100斤大米，为期一年。乙在某一个周三没有送货或送货不符合要求不会实质性影响整个合同，甲可以主张因为这周没有送货的损失，但不能主张乙根本违约。
Often, a contract is clearly indivisible. In such cases, if one party only partially performs, the other party can claim a material breach.
很多时候合同明显是不能分割的，这时如果一方只部分履行，对方就可以主张根本违约。
"Building three identical barns" can usually be claimed as a divisible contract, so if the builder stops working after completing one, they can demand that the owner pay the construction fee for one barn, minus the damages caused by the breach.
“建造三个一模一样的谷仓”通常可以主张分割合同，所以如果建设完一个后不干了，可以要求甲方支付一个谷仓的工程费，减去违约造成的损失。
For "building three identical barns," if the builder asks the owner to pay after completing one, the owner can refuse to pay. The usual rule for common law contracts is that the owner has no duty to pay until the builder has fully performed.
“建造三个一模一样的谷仓”，如果是总价合同（lump sum），建设完一个后让甲方付款，甲方可以拒绝支付。普通法合同通常的约定是乙方履行完毕之后甲方才有义务付款。
"Building half a house" cannot be claimed as a divisible contract, so if the builder stops working halfway, they cannot demand payment from the owner.
“把房子建到一半”不可以主张分割合同，所以如果建设到一半后不干了，不能要求甲方支付费用。
An agreement to deliver parts of a large machine in installments, where the failure to deliver a certain installment makes the entire machine impossible to assemble, clearly constitutes a material breach.
约定每期送货大型机器的一部分零件，缺送某期零件导致整个机器无法组装显然构成根本违约。
The perfect tender rule is different for installment contracts for the sale of goods:
分期货物买卖合同的完美交货规则有所不同：
A bakery bakes bread every Tuesday, and agrees with a seller to deliver a batch of flour before noon every Monday. If for a certain installment the seller promises to deliver on Monday evening, which does not substantially impair the price, it is an acceptable cure, and the bakery should accept it. However, if for a certain installment the seller promises to deliver on Wednesday, because it cannot be cured, the bakery may reject it and claim damages for that installment. But in any case, it does not affect the entire installment contract.
面包房每周二烤面包，约定卖家每周一中午之前送一批面粉。如果某期卖家承诺周一晚上送货，没有严重影响价格，也属于可以接受的弥补，面包房应当接受。但如果某期承诺周三送货，因为无法被补救，面包房可以不接受，并主张当期的损害赔偿。但无论如何，不影响整个分期合同。
The buyer and seller agree to deliver every Wednesday. One week, the seller delivers on Friday, and the buyer still accepts the goods without objection. This does not mean that the seller can deliver on Friday every week thereafter.
买卖双方约定每周三交货，某周卖方周五才交货，买家依然接受了货物且没有提出异议，这并不代表以后每一周卖方都可以周五交货。
However, if the jury finds that Friday deliveries over a sufficiently long period have constituted a modification of the contract by conduct, and the seller has made arrangements in reliance on this, then subsequent Friday deliveries will no longer constitute a breach.
但是，如果陪审团认为足够长时间的周五交货已经构成了通过行为修改合同，且卖家基于对此的信赖作出了安排，那么随后的周五交付将不再构成违约。
签收、拒收、撤销收货Acceptance, Rejection, and Revocation of Acceptance
We need to understand the differences between acceptance, rejection, and revocation of acceptance. Acceptance is different from delivery, which is simply placing the goods outside the buyer's door; delivery does not mean the buyer necessarily accepts the goods. The buyer has the right to decide whether to accept or reject the goods within a reasonable time after delivery. As long as the goods fail to conform to the perfect tender rule, the buyer has the right to reject them.
我们要了解签收（acceptance），拒收（rejection）和撤销签收（revocation of acceptance）的区别。签收和货物放在了买家门外的送达（deliver）有区别，并不是货物送达后就意味着买家必然接受货物（签收，acceptance）。买家有权在货物送达（deliver）后合理时间内决定签收（acceptance）还是拒收（rejection）。只要货物不符合完美送货规则，买家就有权拒收。
In rare circumstances, a buyer may still revoke acceptance after accepting the goods:
在极少数情况下，买家在收货之后依然可以撤销收货：
If the goods fail to conform to the perfect tender rule, even if the buyer accepts them and does not return them, it does not mean they waive the right to claim damages.
如果货物不符合完美交货规则（perfect tender rule），那么即使买家签收后没有退回，也不代表他放弃主张损害赔偿。但是，买方在发现违约后必须在合理时间内通知卖方，否则将丧失任何救济权利。
不安抗辩Adequate Assurance of Performance
If the other party unequivocally indicates that they will breach the contract (anticipatory repudiation), the aggrieved party may:
如果对方明确表示即将违约（anticipatory repudiation），则受影响的一方可以：
A party may retract their previous anticipatory repudiation, unless:
一方可以撤回自己此前即将违约的声明，除非：
If there are reasonable grounds for insecurity regarding the other party's performance, the aggrieved party may demand in writing adequate assurance of due performance within a reasonable time. If the assurance is not provided on time, it may be treated as an anticipatory repudiation. Note that:
如果有理由相信对方无法履行合同，受影响的一方可以书面要求对方在合理时间内提供履约保证，如果不能按时提供保证，可以视为即将违约。需要注意的是：
Anticipatory repudiation must be unequivocal. Merely stating, "I might not be able to perform the contract," at most gives the other party reasonable grounds for insecurity to demand adequate assurance, but does not directly constitute an anticipatory repudiation.
预期违约必须十分明确，仅仅说：“我可能没有能力履行合同”，顶多让对方有理由相信已经无法履行合同，而要求提供担保，并不直接构成预期违约。
Anticipatory repudiation does not necessarily have to be verbal. A sells a rare used car to B, but before delivery, sells and delivers it to C. Although A makes no verbal statement, the intention not to deliver the car to B is unequivocally clear, constituting an anticipatory repudiation.
预期违约并非一定要通过言语。甲出售一辆稀有的二手车给乙，并在交付之前又出售并交付给了丙，虽然甲没有任何言语表示，但不打算交付车给乙的意思已经十分明确，构成预期违约。
条件抗辩Conditions
If a contract specifies that it only becomes effective after a certain condition is met (condition precedent), that condition must be perfectly satisfied; mere "substantial performance" is not enough.
如果合同约定了在某项条件达成之后才生效（condition precedent），则该条件必须完美达成，仅仅“实质性达成”是不够的。
A buyer and a seller agree that the contract is formed only if the buyer obtains a loan with an annualized interest rate of 4%. The buyer can only obtain an interest rate of 4.25%. Although this rate would not substantially affect their standard of living and is very close to 4%, the buyer can still refuse to perform the contract.
买卖双方约定只有在买方获得年化4%利率的贷款时合同才成立，买方只能获得4.25%的利率，该利率不会实质性影响他的生活水平，且与4%相差无几，但买方依然可以拒绝履行合同。
The testing points for conditions are relatively fixed. For example, the protected party may waive the condition, while the unprotected party cannot refuse the transaction on the grounds that the condition was not met.
条件抗辩的考点比较固定。比如，受保护的一方可以免除（waive）合同条件，而没有被保护的一方不得以条件没有达成拒绝交易。
As above, the buyer can only obtain a 4.25% interest rate. However, this time the buyer is willing to waive the 4% condition and bear the higher interest rate and monthly payments. The seller cannot refuse the transaction. Because regardless of the buyer's interest rate, the seller receives the full purchase price in a lump sum. The interest rate clause is designed to protect the buyer, and the buyer's waiver has no impact on the seller.
同上，买方只能获得4.25%的利率。但这次买方愿意豁免4%的条件，承担更高的利率和月供。卖家不能拒绝交易。因为无论买方利率为多少，卖家都是一次性获得全部购房款，利率条款是为了保护买方，买方的豁免对卖方没有任何影响。
As above, the buyer's credit history is too poor to obtain any loan, but they suddenly win the lottery and are willing to buy the house in full with cash. The seller cannot refuse the transaction.
同上，买方的信用记录太差无法获得任何贷款，但他突然中了彩票愿意全款买房。卖家不能拒绝交易。
Another example is that both parties to the contract must actively facilitate the fulfillment of the condition.
又比如，合同双方必须积极促进条件的达成。
A buyer and a seller agree that the contract is formed only if the buyer obtains a loan with an annualized interest rate of 4%. After signing, the buyer intentionally seeks to breach the contract and deliberately reports their financial condition very poorly, leading the bank to predictably deny the loan. The buyer has negatively interfered with the fulfillment of the contract condition and cannot assert the failure of the condition as a defense.
买卖双方约定只有在买方获得年化4%利率的贷款时合同才成立，签约后买家存心违约，故意将自己的条件申报地非常恶劣，银行果然拒绝贷款。买方消极影响合同条件的达成，不能主张合同的条件抗辩。
Finally, condition subsequent is occasionally tested, which means that if a certain condition occurs, a party is discharged from their contractual obligations.
最后，偶尔会考到后置条件（condition subsequent），是指如果达到某个条件，一方免除合同义务。
We must distinguish between a condition and a promise. Failure to fulfill a promise results in a breach of contract. However, the result of a condition not being met is that performance is not required or is discharged, which does not constitute a breach.
我们要区分条件和承诺（promise），后者没有达成会造成违约。而条件没有达成的结果是不必履行，或者免除履行，不构成违约。
A programmer sells their completed program to a software promoter. Just as the software promoter finishes debugging and is ready to launch, they discover that the programmer has already released a similar competing product. The programmer has violated an implied promise in the sales contract, constituting a breach.
程序员将自己写好的程序卖给软件推广商，就在软件推广商调试好准备上线时，发现程序员已经推出了类似的竞品。程序员违反了销售合同中隐含的承诺（implied promise），构成违约。
不可抗力Excuse of Performance (Impossibility, Impracticability, and Frustration of Purpose)
If, after a contract is made, an unforeseeable event occurs that makes a party's performance impossible (impossibility), practicable but highly impractical (impracticability), or destroys the principal purpose of the contract for either party (frustration of purpose), that party may claim to be excused from performance.
合同签订后如果发生了双方都无法预期的事情导致合同的任何一方不可能履行（impossibility）、虽然可能履行但不切实际（impracticability）或者任何一方的合同的目的不再有意义（frustration of purpose），则该方可以主张免除履行责任。
Generally, the death of a party does not terminate a contract, such as a real estate sales contract. However, if the contract is closely related to the unique characteristics of a party, it will be discharged. For example, a student cannot require the executor of a deceased tutor's estate to perform the contract, because tutoring services are unique.
通常合同一方的死亡不会导致合同失效，比如房屋买卖合同。但如果合同与一方的特质密切相关，比如学生不能要求家教老师的遗产管理人代为执行合同，因为家教服务是独一无二的。
A and B enter into a contract for the sale of marijuana. Subsequently, the state declares marijuana transactions illegal. This constitutes impossibility of performance, and both parties' contractual duties are discharged.
甲乙签订交易大麻的合同，随后该州宣布大麻交易违法，这是不可能履行，双方的合同义务解除。
A and B enter into a contract for the sale of marijuana. Unbeknownst to them, marijuana transactions are already illegal in the state. This is a contract formed for an illegal purpose, making the contract void.
甲乙签订交易大麻的合同，他们不知道的是，大麻交易在该州是违法的。这是以违法为目的订立的合同，合同无效。
A and B enter into a contract for the sale of crude oil. Subsequently, a war breaks out in B's country, making it impossible to supply crude oil. Although B could still purchase crude oil from elsewhere to trade with A, doing so would be commercially impracticable. B's contractual duties may be discharged.
甲乙签订交易原油的合同，随后乙所在的国家战争爆发导致无法供应原油。虽然乙依然可以从其他地方购买原油和甲交易，但如果从其他地方购买的成本极其高昂，导致履行变得极端困难和不合理，这就属于不切实际的履行。乙可以解除合同义务。
A and B enter into a contract for the sale of crude oil, agreeing to use the real-time oil price published by a certain agency as the transaction price. Later, the agency is abolished. This contract can still be performed; the missing price term can simply be supplied by the UCC's 'reasonable price' gap-filler.
甲乙签订交易原油的合同，约定以某机构发布的实时油价为交易价格，后该机构被撤销。这是可以继续履行的合同，用UCC“合理价格”的条款进行补足即可。
A and B enter into a construction contract. Subsequently, A discovers a layer of rock under the site that is very difficult to excavate. If such rock layers are not uncommon on construction sites, A cannot claim that performance is impracticable. Note that claiming impossibility, impracticability, or frustration of purpose all require that the newly occurred event was unforeseeable by both parties at the time of contracting.
甲乙签订建筑合同，随后甲发现工地下面有一块非常难挖的岩土层。如果该岩土层在建筑工地上并不罕见，甲并不能主张履行合同不切实际。注意，主张不可能履行（impossibility）、履行不切实际（impracticability）或者合同的目的不再有意义（frustration）都要求该事件的不发生是双方订立合同的基本假设（通常表现为无法预见）。
A leases B's stadium to use as a mask warehouse. Later, the government requisitions all masks. The purpose of the contract is frustrated.
甲租赁乙的体育馆用作口罩仓库，后政府征用了所有口罩，合同的目的不再有意义。
A leases B's stadium to use as a mask warehouse. Later, the government requisitions the stadium to use as a makeshift hospital. This constitutes impossibility of performance.
甲租赁乙的体育馆用作口罩仓库，后政府征用了体育馆用作方舱医院，这是不可能履行。
A leases B's stadium to use as a mask warehouse. Unbeknownst to them, the government has already requisitioned the stadium to use as a makeshift hospital. This is a misunderstanding by both parties regarding a fact that materially affects the contract at the time of formation, which constitutes a mutual mistake. In contrast, claims such as impossibility are based on new events occurring after the contract is signed.
甲租赁乙的体育馆用作口罩仓库，他们不知道的是政府已经征用体育馆用作方舱医院。这是在合同成立时双方对实质性影响合同的事实有误解，是共同误解（mutual mistake）。而不可能履行等主张是依据合同签订后新发生的事件。
和解清偿协议Accord and Satisfaction
An accord is an agreement under which a party accepts a new performance in substitute for the original contractual duty. If the new performance is of a different type, we allow its actual value to be lower than that of the original contractual duty.
和解清偿协议（accord）是指用新的履行来替代原本的合同义务。如果是不同的履行方式，我们允许其实际价值比原本的合同义务要低一些。
A owes B 100,000. A and B agree that A will settle the debt with an antique belonging to A. Although the market value of the antique is only 80,000, the accord is enforceable.
甲欠乙10万，甲乙约定用甲的一件古董清偿。虽然古董市价只值8万，但和解清偿协议可以执行。
If the performance is of the exact same type, we generally only allow the accord to be enforceable when there is a good faith dispute between the parties. Simply put, an accord must satisfy the doctrine of consideration.
如果完全是相同的履行方式，我们通常只允许当双方有实际争议（good faith dispute）时，和解清偿协议才可以执行。简单来说，和解清偿协议需要符合对价理论。
A owes B 100,000. The parties enter into an accord agreeing that A only needs to repay 80,000. There is no dispute between the parties regarding the debt. This agreement does not satisfy the doctrine of consideration.
甲欠乙10万，双方签订和解清偿协议约定甲只用还8万，双方对债务没有任何争议，该协议不符合对价理论。
It is important to distinguish an accord from a contract modification: an accord does not discharge the original contract; it merely suspends the execution of the original contract. If the obligor breaches the accord, the obligee may sue on either the original contract or the accord.
需要和合同的修改区分的是，和解清偿协议并没有废除原来的合同，只是暂停原来合同的执行。如果义务方违约，权利方既可以执行原合同，也可以执行和解清偿协议。
A owes B 100,000. A and B agree that A will settle the debt with an antique belonging to A. A fails to deliver the antique on time. B can either demand A to repay the 100,000 or demand A to deliver the antique.
甲欠乙10万，甲乙约定用甲的一件古董清偿。甲没有如期交付古董，乙既可以要求甲偿还10万，也可以要求甲交付古董。
The performance of the accord (satisfaction) discharges not only the original contractual duty but also the duty under the accord. We generally use the term 'accord and satisfaction' to describe this process.
和解清偿协议的履行（satisfaction）不仅解除了原本的合同义务，也解除了合同清偿协议的义务。一般我们会用accord and satisfaction表示这个过程。
If the obligee reneges, the obligor can use the accord as a defense.
如果合同权利方反悔，义务方可以用和解清偿协议作为抗辩，甚至可以反诉要求强制执行和解协议和赔偿。
A owes B 100,000, which is already due. A and B agree that A will settle the debt with an antique one year later. Shortly after, B reneges, refusing the antique and demanding the 100,000 instead. A can use the accord as a defense.
甲欠乙10万已经到期，甲乙约定一年后用甲的一件古董清偿。不久后乙反悔，不要古董，而是要10万，甲可以用和解清偿协议作为抗辩。
弃权Release
The relinquishment of contractual rights (release) or the right to sue (covenant not to sue) also requires consideration under the common law, and usually must be in writing. Under the UCC, however, consideration is not required.
合同权利的放弃（release）或诉讼权利的放弃（contract not to sue）同样需要符合对价理论，通常还需要书面。UCC下则不需要对价。
We need to distinguish between a release and the performance of an accord (satisfaction). The former is a complete relinquishment of a right, while the latter is the acceptance of an alternative method of performance.
我们需要把弃权（release）和清偿协议的履行（satisfaction）区分开来，前者是完全放弃权利，后者是对替代履行方式的认可。
We have tabulated several easily confused concepts related to consideration:
我们把几个和对价相关、容易混淆的概念列成表格：
| Common Law | UCC | |
|---|---|---|
| Irrevocable Offer | (Option Contract) | (Firm Offer) No consideration required, writing required |
| Irrevocable Offer | Consideration required, no writing required | Max 3 months without consideration |
| Contract Modification | Consideration required, no writing required | No consideration required, no writing required, but must be in good faith |
| Release | Consideration required, writing required | No consideration required, writing required |
| 普通法 | UCC | |
|---|---|---|
| 不可撤销的要约 | (Option Contract) | (Firm Offer) 不需要对价，需要书面 |
| 不可撤销的要约 | 需要对价，不需要书面 | 没有对价最多3个月 |
| 修改合同 Modification | 需要对价，不需要书面 | 不需要对价，不需要书面，但要基于善意 |
| 弃权Release | 需要对价，需要书面 | 不需要对价，需要书面 |
合同与第三人Contracts and Third Parties
合同相对性Privity of Contract
The United States also recognizes the doctrine of privity of contract, under which non-parties generally cannot assert contractual rights.
美国也有合同相对性理论（privity of contract），非合同方通常不能主张合同权利。
Example: A invests in B's bubble tea shop and loses everything. A cannot sue celebrity C, who advertised the shop, for breach of contract because C is not a party to the contract. However, A might be able to sue the celebrity in tort for misrepresentation. As we can see, the theory of misrepresentation exists in both contract and tort law, and we will study it in detail in the torts section.
甲投资乙奶茶店后血本无归，甲不能主张为奶茶店打广告的丙明星违约，因为丙不是合同方。但甲或许可以主张明星侵权，案由是虚假陈述（misrepresentation），可以看到，合同篇和侵权篇都有虚假陈述理论，我们还会在侵权篇详细学习。
受益第三人Third-Party Beneficiaries
Third-party beneficiaries are an exception to the privity of contract. The most frequently tested concepts are intended beneficiaries and incidental beneficiaries. The reason I translate it this way is that the third party must appear in the contract; otherwise, no matter how tailor-made the contract is for them, they are not a proper party to sue for breach.
受益第三人是合同相对性的例外。其最热门的考点是故意受益第三人（intended beneficiary）和附带受益第三人（incidental beneficiary）。合同必须体现出让第三人直接受益的意图，否则无论该合同是多么地量身定做，他也不是主张违约的适格主体。
A hospital and a cleaning company enter into a contract to disinfect hospital rooms, but inadequate disinfection leads to a patient getting infected. Although cleaning the rooms is obviously for the patients' health, because the patient is not mentioned in the contract, they are not an intended beneficiary. The patient might be able to sue the cleaning company in tort, but cannot sue for breach of contract.
医院和清洁公司签订给病房消毒的合同，结果消毒不到位导致病人被感染。虽然清洁病房显然是为了病人的健康，但因为病人没有在合同上，他不是故意受益第三人。病人或许可以主张清洁公司侵权，但无法主张违约。
Example: A hospital and a cleaning company enter into a contract to disinfect hospital rooms, and the contract explicitly states that the cleaning contract is for the health of the patients in the rooms. Although the patients' names are not on the contract (unnamed), and it may not even be known who the patients are at present, an affected patient can sue for breach of contract.
医院和清洁公司签订给病房消毒的合同，合同中明确注明，清洁合同是为了病房病人的健康。虽然病人的名字没有在合同上（unnamed），甚至现在都不知道病人是谁，但是受到影响的病人可以主张违约。
Example: After a tenant breaks the landlord's window, the tenant contracts with a business to repair the landlord's window. The landlord is a proper party to sue the business for breach of contract.
房客打碎了房东的窗户后与商家签约维修房东的窗户，房东是起诉商家违约的适格主体。
After determining that a third-party beneficiary is an intended beneficiary, we must see whether their contractual rights have vested. If the third party's interests have not vested, the original contracting parties can mutually agree to modify the contract. A third party can vest their interests in the following ways:
在确定受益第三人为故意受益第三人后，我们要看看他的合同权利是否是既定的（vested），如果第三人的利益没有既定，则合同双方可以合意修改合同。第三人可以通过以下方式让自己的利益既定：
Example: A and B agree to build a house for C. C knows about this but does not express assent. A and B can mutually agree to modify or cancel the contract.
甲和乙约定给丙修建一栋房屋，丙知道此事却没有表态，甲乙可以合意修改或取消合同。
Example: A and B agree to build a house for C. After learning of this, C notifies A and B in writing and happily accepts the house. C now has a vested right, and A and B can no longer impair C's interests as an intended third-party beneficiary.
甲和乙约定给丙修建一栋房屋，丙知道此事后书面告知甲和乙并欣然接受这一栋房屋。丙此时有了既定的权利（vested right），甲和乙不能再损害丙作为故意受益第三人的利益。
权利转让Assignment of Rights
Under common law, contract rights are generally assignable by default without the consent of the other party. Even if a contract merely states "no assignment of the contract," this is construed as barring only the delegation of duties, not the assignment of rights. Only when a contract explicitly prohibits the assignment of rights ("no assignment of rights") is the assignor barred from assigning them.
在普通法中，合同的权利默认都是可以转让的（assignment of rights），不需要经过另一方同意。甚至合同仅仅是禁止转让（no assignment of the contract），禁止的也只是义务的转让而不是权利的转让。只有合同明确禁止转让权利（no assignment of rights），转让方（assignor）才禁止转让权利。
If a contract prohibits the assignment of rights, but the assignor insists on assigning them and the obligor follows instructions to perform for the third party, it can be considered that the contract was modified by subsequent mutual assent, or that the obligor made arrangements based on reliance on the assignor's words. Of course, the more prudent approach for the obligor is to ignore the assignment.
合同禁止转让权利，转让方执意转让，义务方听从指示履行给第三人。可以认为合同通过后续的合意修改，也可以认为义务方基于对转让方言语的信赖作出了安排。当然，义务方更谨慎的做法是无视转让。
Gratuitous assignments (without consideration) are generally revocable, unless the obligor has already performed for the assignee (the third party), or the assignee has detrimentally relied on the assignment. Assignments for consideration cannot be unilaterally revoked.
没有对价的转让通常可以撤销，除非合同的义务方已经履行给被转让方（第三方，assignee），或者被转让方基于对转让的信赖作出了安排，或者该转让是通过交付象征性凭证（如存折、股票）或书面转让文件完成的。有对价的转让不可以单方面撤销。
For example, A gives B A's passbook and states that A is giving the deposit to B. This gratuitous assignment completed by delivery of a symbolic token is irrevocable.
例如，甲将自己的存折交给乙，表示将存款赠与乙，这种通过交付象征性凭证完成的无对价转让是不可撤销的。
义务转让Delegation of Duties
If the spirit of contract interpretation is to encourage the assignment of rights, the interpretation of the delegation of duties is much more restrictive. Although contracts also do not prohibit the delegation of duties by default:
如果说解释合同的精神是鼓励转让权利，那转让义务（delegation of duties）的解释就要限缩很多。虽然合同默认也是不禁止转让义务，但：
A contracts with B to design A's house, as A values B's specific decorating style and taste. Even though C has a very similar style and taste to B, and the contract does not expressly prohibit delegation, B cannot delegate his contractual duties to C without A's consent.
甲签订合同让乙设计自己的房屋，甲看中的是乙特定的装修风格和品位，虽然丙和乙有十分类似的风格和品位，合同也没有明文禁止转让，乙也不能不经过甲同意就把自己的合同义务转让给丙。
A delegation of duties can be viewed as a separate contract. If the new obligor (the third party, delegatee) breaches, the delegator can claim damages.
转让义务可以视为一个单独的合同，如果新的义务人（第三方，delegatee）违约，转让方（delegator）可以主张损害赔偿。
However, delegating a duty does not relieve the delegator of their own contractual liability. Therefore, if the delegatee breaches, the original obligee of the contract can also claim damages from the delegator.
但转让义务并不能免除转让方自己的合同责任。所以如果被转让方违约，合同原本的权利方也可以向转让方主张损害赔偿。
Can the original obligee of the contract assert rights against the delegatee? There seems to be no privity of contract. However, we can resolve this issue using previously learned theories. In the new delegation contract, the original obligee is an intended third-party beneficiary and has the right to sue for breach.
合同原本的权利方是否可以向被转让方主张权利呢？似乎没有合同相对性。但我们可以用之前学过的理论来解决这个问题。在新的转让合同中，合同原本的权利方是故意的受益第三人，有权主张违约。
约务更替Novation
Novation is very similar to the delegation of duties, but fundamentally different. Delegation generally does not require the consent of the other party to the contract, whereas novation involves all three parties signing a new contract to completely replace the previous bilateral contract. Under the theory of novation, the original contractual rights and duties cease to exist.
约务更替（novation）与义务的转让（delegation）非常类似，但有本质不同。转让通常不需要合同的另一方同意，约务更替则是三方重新签署一个新的合同完全替代此前的双方合同。在约务更替理论下，原本的合同权利和义务不复存在。
Novation also differs significantly from the previously discussed accord and satisfaction: novation introduces a third party and does not require consideration of the theory of consideration.
约务更替和前文的和解清偿协议（accord and satisfaction）也有较大的区别：约务更替引入了第三方，也不用考虑对价理论。
| Consent | Consideration | Original Contract | |
|---|---|---|---|
| Delegation | Unilateral | Existing consideration | Exists |
| Accord | Bilateral | Required | Exists (suspended) |
| Novation | Trilateral | Not required | Replaced |
| 同意 | 对价 | 原合同 | |
|---|---|---|---|
| 义务转让 delegation | 单方 | 既有对价 | 存在 |
| 和解清偿协议 accord | 双方 | 需要 | 存在（暂停执行） |
| 约务更替 novation | 三方 | 不需要 | 被替代 |
违约和普通法救济Breach and Common Law Remedies
附带赔偿金Incidental Damages
Incidental damages refer to the reasonable expenses incurred by the non-breaching party as a result of the breach, such as costs for inspection, transportation, care, and resale.
附带赔偿金（incidental damages）是指守约方为违约行为付出的检测、运输、保管、转卖等花费的合理费用。
Because the seller breached, the buyer consulted a lawyer to ask what he should do, and upon the lawyer's advice, hired a purchasing agent to buy goods at the same price on the market. The fees charged by the lawyer and the purchasing agent are incidental damages. Similar to China, unless agreed upon in advance by both parties, attorney's fees are generally not awarded by the court. In exam questions, please do not calculate attorney's fees unless there is an agreement.
因卖家违约，买家咨询律师询问他应该做什么，并在律师的建议下聘请采购员在市场上购买到了价格一样的商品。律师、采购员收取的费用就是附带赔偿金。和中国一样，除非双方提前约定，律师费用通常不会被法院支持。在题目中，没有约定的情况下请不要计算律师费用。
Although incidental damages do not require a strict foreseeability test, for the convenience of the exam, we can assume when answering questions that: all common law damages require foreseeability. Furthermore, oral or written communications prior to the signing of the contract can be used to prove that the damages were foreseeable, and are not restricted by the parol evidence rule.
附带赔偿金虽然不用进行严格的可预见性测试，但为了考试方便，我们做题时可以认为：所有的普通法赔偿金都要求可以预见。并且，在签订合同之前的口头或书面沟通可以用来证明违约金可以预见，不受口头证据规则的限制。
期望赔偿金、后果赔偿金Expectation Damages and Consequential Damages
Expectation damages represent the benefit the non-breaching party would have received had the contract been fully performed.
期望赔偿金（expectation damages）是合同如果顺利履行，守约方可以获得的权益。
A seller delivers goods, and the buyer refuses to pay the 5,000 yuan purchase price. The 5,000 yuan is classic expectation damages.
卖家发货，买家拒不支付货款5000元。5000元就是经典的期望赔偿金。
Different textbooks define expectation damages differently. Some textbooks consider compensatory expectation damages and compensatory consequential damages collectively as compensatory damages. The former is specified within the contract, while the latter results indirectly from outside the contract, including asset appreciation and expected profits from resale to a third party.
不同的教材对期望赔偿金的定义不同。一部分教材认为，期望赔偿金（compensatory expectation damages）和后果赔偿金（compensatory consequential damages）统称为弥补赔偿金（compensatory damages）。前者是合同内注明的，后者是合同外导致间接的，包括资产的增值、转卖给第三方应得的收益。
Some textbooks classify both consequential damages and incidental damages under expectation damages.
部分教材将后果赔偿金、附带赔偿金都归为期望赔偿金。
Some textbooks consider expectation damages to be the additional cost of finding a substitute, while consequential damages are other direct or indirect losses.
部分教材认为期望赔偿金是寻找替代品的额外费用，后果赔偿金是其他直接或间接损失。
Both expectation damages and consequential damages require foreseeability.
期望赔偿金和后果赔偿金都要求可以被预见。
A purchases a batch of apples, but B fails to deliver. A then spends an additional 10,000 yuan to urgently purchase a substitute batch of apples. As long as this cover is made in good faith and without unreasonable delay, it should generally be upheld.
甲采购一批苹果，乙没有发货，甲于是额外支出1万元紧急购买了一批苹果，这种替代只要是善意且没有不合理延迟的，通常都应当被支持。
B sells a house, and A refuses to pay. At the time of the breach, the house has naturally depreciated by 10%. The natural depreciation of a house is generally foreseeable, and B can claim compensation from A for the depreciated amount.
乙出售一套房，甲拒绝付款，在违约时，房子自然贬值了10%。房子的自然贬值一般都可以被预见，乙可以向甲主张赔偿贬值的金额。
信赖赔偿金Reliance Damages
Reliance damages are the expenses incurred by the non-breaching party based on reasonable arrangements made in reliance on the contract. If expectation damages consider the situation after the contract is fully performed, reliance damages consider what the situation would be if the contract had never existed.
信赖赔偿金（reliance damages）是守约方基于对合同的信赖作出的合理安排产生的费用。如果说期望赔偿金考虑的是合同完全履行之后的状况，信赖赔偿金考虑的是如果合同从来没有存在过会是怎样。
Reliance damages also require foreseeability.
信赖赔偿金也要求可以被预见。
Relying on the contractor's ability to finish on time, the developer schedules a grand celebration on the completion date and spends a fortune to hire celebrities to perform. The contractor finishes a week later than the original date, causing huge losses to the developer. If the developer did not inform the contractor of such arrangements in advance, the contractor will most likely not have to pay for such massive losses due to unforeseeability. Typically, losses that are foreseeable even without prior notice include a reasonable week's rent for the project.
基于对承包商能够按时完工的信赖，开发商定于完工之日举办盛大的庆典并斥巨资请了明星驻场。承包商晚于原定日期一周完工，给开放商造成了巨大的损失。如果开发商没有提前告知承包商如此安排，承包商大概率因为无法预见不用支付如此大的损失。通常，不用提前告知也可以预见的损失包括工程项目一周的合理租金。
Relying on the contractor's ability to finish on time, the developer schedules a grand celebration on the completion date and spends a fortune to hire celebrities. The contract specifies that "time is of the essence." The contractor finishes a week late, which constitutes a material breach (failure to substantially perform), so the developer does not have to pay. However, if the developer's losses cannot be covered even by withholding the construction payment, whether the contractor must pay for the additional losses still depends on whether they were foreseeable. In exam questions, this mainly depends on whether the developer informed the contractor of such arrangements in advance.
基于对承包商能够按时完工的信赖，开发商定于完工之日举办盛大的庆典并斥巨资请了明星驻场。合同中注明了时间是紧要的（time is of the essence）。承包商晚于原定日期一周完工，这属于没有实质履行合同，开发商不用付款。但如果对开发商造成的损失即使不支付工程款也无法弥补，承包商是否要支付额外的损失，依然要看他是否可以预见这些损失，在题目中，主要是看开发商有没有提前告知承包商如此安排。
Reliance damages and expectation damages can only be claimed in the alternative.
信赖赔偿金和期望赔偿金只能择一主张。
A purchases a batch of apples, then spends 5,000 yuan on advertising for the apples and pays a 3,000 yuan deposit to hire people to sell them. B fails to deliver the apples, and A can claim 8,000 yuan in reliance damages. A later spends an additional 10,000 yuan to urgently purchase a substitute batch of apples. It can be seen that if A claims this 10,000 yuan, the money spent on advertising and hiring was not wasted. This is why expectation damages and reliance damages can only be claimed in the alternative.
甲采购一批苹果，随后为苹果打了5000元的广告并支付3000元定金雇人销售苹果。乙没有送来苹果，甲可以主张8000元的信赖赔偿金。甲后来又额外支出10000元紧急采购一批苹果，可以发现，如果甲主张这10000元，他打广告和雇人的钱就没有白花，这就是为什么期望赔偿金和信赖赔偿金只能择一主张。
赔偿金的组合Combination of Damages
We also require that even the non-breaching party must take certain measures to mitigate damages.
我们还要求即使是守约方，也需要采取一定的措施减少损失。
The formula for calculating common law damages in mainstream textbooks is:
主流教材普通法赔偿金的计算公式是：
(Expectation Damages / Reliance Damages) + Consequential Damages + Incidental Damages - Losses that could be reasonably avoided
（期望赔偿金/信赖赔偿金） + 后果赔偿金 + 附带赔偿金 - 可以合理减少的损失
Note that all of these must be foreseeable.
注意这些都必须是可以预见的。
A buyer orders a computer host and specifically purchases a 2,000 yuan monitor for it (reliance damages). If the assembled computer can be sold, a reasonable profit of 5,000 yuan can be made. The seller refuses to deliver the host, and the buyer urgently purchases a substitute host, spending an extra 1,000 yuan (expectation or consequential damages), and incurs an extra 100 yuan in phone bills and advertising fees for contacting the substitute supplier (incidental damages). However, since the computer is successfully assembled, the monitor originally prepared is not wasted, so reliance damages can no longer be claimed. The 5,000 yuan profit can still be earned, so this fee cannot be claimed again. It is generally believed that if a substitute host ultimately cannot be found, the 5,000 yuan reasonable profit can be claimed. Some textbooks consider this expectation damages, which cannot be claimed together with the 2,000 yuan for the monitor (reliance damages). However, the mainstream view is that if the monitor cannot be resold to mitigate losses, both the 5,000 yuan and the 2,000 yuan are the buyer's losses and can be claimed together. In this case, the 5,000 yuan can be viewed as consequential damages, thereby bypassing the unfairness of having to choose between expectation and reliance damages.
买家订购了一台电脑主机，为此专门采购了一台2000元的显示器（信赖赔偿金），如果能卖出组装电脑，可以赚5000元的合理利润。卖家拒绝发货主机，买家紧急采购替代主机，额外花费1000元（期望或后果赔偿金），额外联络采购产生的电话费、广告费等100元（附带赔偿金）。但既然电脑顺利组装，本来准备的显示器就没有白费，所以不能再主张信赖赔偿金。本来赚的5000元依然也可以赚到，所以不能再主张这个费用。普遍认为，如果最终没有能找到替代的主机，合理利润5000元是可以主张的。部分教材认为这是期望赔偿金，不能和显示器的2000元（信赖赔偿金）一并主张。但主流观点认为，如果无法转卖显示器减少损失，5000元和2000元都是买家的损失，可以一并主张，此时可以将5000元视为后果赔偿金，从而绕开期望和信赖二选一的不公平。
Following the above example, if the buyer could clearly have resold the monitor to mitigate the loss by 1,500 yuan but failed to do so, the buyer must bear this 1,500 yuan.
同上例，如果买家明明可以转卖显示器减少1500元损失却没有转卖，这1500元由买家承担。
The calculation method for damages is very similar to China's Civil Code. The equity law to be discussed later is even more similar to China's Civil Code. Therefore, using a simple sense of justice to solve damage calculation questions in the MBE is a good approach. Since mainstream textbooks disagree on the classification of damages, exam questions will most likely only ask you to calculate the amount rather than classify them.
损害赔偿的计算方法和中国的民法典很像。后面会讲到的衡平法和中国民法典更像。所以，MBE中计算损失用朴素的正义感做题是不错的办法。既然主流教材关于赔偿金的分类有分歧，题目也大概率只会让你算数，而不会让你分类。
约定赔偿金Liquidated Damages
U.S. courts also apply the "make-whole" principle to breaches of contract, meaning the breaching party compensates the non-breaching party rather than being punished. If liquidated damages are deemed a penalty against the breaching party, courts will not enforce them. Under common law, liquidated damages must satisfy the following:
美国的法院处理违约同样适用“填平原则”，即违约方对守约方的填补，而不是惩罚违约方。如果约定赔偿金（liquidated damages）被视为对违约方的惩罚，法院不会执行。在普通法下，约定赔偿金必须满足：
Under the UCC, if the liquidated damages were not a reasonable forecast of the loss at the time of contract formation but accurately reflect the actual damages caused by the breach, courts may still enforce them.
在UCC下，如果约定赔偿金并非合同签订时对损失的合理预计，但准确反应了因违约造成的实际损失，法院也可以执行。
惩罚性赔偿和象征性赔偿Punitive Damages and Nominal Damages
We will see many instances of punitive damages and nominal damages in tort law. Punitive damages are used to punish wrongful acts and are uncommon in contract law. However, if a party cannot prove any actual loss but merely wants to claim $1 in nominal damages to establish that the other party breached the contract, the court may award nominal damages.
我们会在侵权中见到很多惩罚性赔偿（punitive damages）和象征性赔偿（nominal damages）。惩罚性赔偿用于惩罚恶意行为（wrongful act），在合同法中并不常见。但如果一方无法主张任何损失，仅仅想主张1美元的象征性赔偿证明对方违约，法院可以支持象征性赔偿。
雇佣合同的注意事项Considerations for Employment Contracts
On the MBE, we apply basic contract law—namely, the common law—to handle employment disputes. If an employment contract does not specify a duration (at-will employment), the employer can terminate the employee at any time without additional compensation.
在MBE考试中，我们用朴素的合同法，即普通法来处理劳动争议。如果劳动合同没有设定期限（at will），雇主可以随时解雇劳工而不用额外赔偿。
However, if the employment contract specifies a duration, the employer cannot terminate the contract early without cause; otherwise, they must pay the salary for the remaining term. Nevertheless, the employee must also make an effort to find another job to mitigate this loss. A frequently tested point is that the employee is only required to seek comparable employment, not just any income-generating job.
但如果劳动合同设立的期限，雇主就不能无故提前解除合约，否则需要支付剩余期限的薪水。但员工也应该努力找工作降低这个损失。常考的是，员工只需要找类似的工作，而不需要找任何可以带来收入的工作。
Example: A signs an agreement to work as a trainee lawyer for B for one year at a monthly salary of $3,000. After two months of work, B terminates A without cause. A is a top graduate from a prestigious university and could easily find a job as a nanny paying $30,000 a month, but he is unwilling to do so. Ultimately, he can only find a trainee lawyer position paying $2,500 a month. Whether or not A accepts the $2,500 trainee lawyer job, B must compensate A for the salary difference over the remaining 10 months, which is $5,000. If A is completely unable to find another trainee lawyer job, B must compensate A for the full 10 months' salary, totaling $30,000.
甲签订协议在乙处担任实习律师一年，月薪3000元，工作两个月后乙无故解雇了甲。甲是名牌大学高材生，可以轻松找到月薪30000元的保姆工作，但他不愿意去做保姆，最后只能找到月薪2500元的实习律师工作。无论甲接不接受该2500元的实习律师工作，乙需要赔偿10个月的工资差价5000元。如果甲始终找不到实习律师的工作，乙需要赔偿10个月的工资30000元。
Example: Following the previous example, if A accepts the nanny job, he is deemed to have suffered no loss and may no longer claim damages.
同上例，如果甲接受了保姆工作，视为没有损失，不得再主张赔偿。
If an employee resigns early without cause, the employer can similarly claim damages.
员工无故提前离职，雇主也同样可以主张损害赔偿。
Example: A signs an agreement to work as a programmer for B for one year at a monthly salary of $30,000. After two months, A resigns without cause. B reasonably incurs an additional $1,000 to hire another programmer at a monthly salary of $40,000. B can claim the $1,000 recruitment cost and the salary difference of $10,000 per month for the remaining 10 months.
甲签订协议在乙处担任程序员一年，月薪3万元，工作两个月后甲无故离职。乙合理地额外花费1000元招聘了另外一名程序员，月薪4万元。乙可以主张1000元的招聘成本和10个月、每月1万元的工资差价。
These rules differ significantly from Chinese labor law and require special attention.
这些和中国的劳动法区别很大，需要注意。
货物买卖合同的注意事项Considerations for Contracts for the Sale of Goods
The various remedial principles of common law also apply to contracts for the sale of goods. However, the UCC provides specific rules for the details. When a buyer breaches, the seller can claim the difference in price based on the actual resale price.
普通法的各项救济原则同样也适用于货物买卖合同。但UCC对细节进行了一些规定。买方违约时，卖方可以按照实际的转卖价格主张差价损失。
Example: Graphics card prices once fluctuated wildly. A buyer purchases a batch of used graphics cards from a seller, but later breaches the contract, forcing the seller to resell them. At the time of contract formation, the graphics cards were worth $2,000 each, and the contract price was $2,500 each. At the agreed time of delivery, the value dropped to $1,500 each, and the seller resold them for $1,000 each. Assuming such massive fluctuations in the used graphics card market were foreseeable, the seller can claim a price difference of $2,500 - $1,000 = $1,500 per card. If the seller chooses not to resell, they can claim a price difference of $2,500 - $1,500 = $1,000 per card.
显卡的价格波动一度非常剧烈。买家向卖家采购一批二手显卡，后买家违约，卖家不得不转卖这些显卡。在签订合同时，显卡价值2000美元/块，合同约定2500美元/块，在约定的交付期时，显卡价值1500美元/块，卖家转卖的价格是1000美元/块。假设二手显卡市场如此大的波动是可以预见的，则卖家可以主张2500-1000=1500美元/块的差价。如果卖家选择不转卖，则可以主张2500-1500=1000美元/块的差价。
If the seller has a large volume of identical goods and can easily resell them at the same price, the seller can claim the lost profits from the sale.
如果是大量同样商品的卖家，以同样的价格转卖会很容易，此时卖家可以主张销售可得的利润。
Example: Gates contracts to purchase 100 iPhones from Cook but then breaches. Although Cook can easily sell the phones to someone else at the same price, he can still claim the lost profits on the 100 iPhones.
盖茨向库克采购100台苹果手机后违约。库克虽然可以很容易地将手机以相同的价格卖给他人，但依然可以主张100台苹果手机的利润。
衡平法和衡平法救济Equity and Equitable Remedies
衡平法概述Overview of Equity
I have briefly mentioned some aspects of equity earlier without going into detail. For Chinese examinees, introducing equity abruptly within common law topics can be quite jarring, so I plan to dedicate a separate chapter to it. Article III, Section 2 of the U.S. Constitution states that the judicial power of the United States extends to all cases "in Law and Equity" arising under the Constitution, placing common law and equity on equal footing and indicating that they are two very distinct systems.
我在前面零散提到了一些衡平法的内容但没有细讲。对中国考生来说，冷不丁在普通法内容中介绍衡平法会非常突兀，所以我打算单独用一章来讲衡平法。美国宪法第3条第2款表明合众国的司法权覆盖所有“普通法和衡平法”的案子（The judicial Power shall extend to all Cases, in Law and Equity, arising under this Constitution...），把普通法和衡平法放到了并列的位置，说明这是两套很不相同的系统。
Civil law systems generally do not strictly follow precedent, and English equity shared a similar characteristic at its inception: if strictly following precedent could not yield a fair result, the common law would be bypassed, and cases would be decided based on the judge's discretionary concept of fairness. U.S. law shares the same lineage as English law, and equity is similarly widely applied in the United States, with Article III, Section 2 of the Constitution providing explicit constitutional backing for its application.
大陆法系普遍不必完全遵循先例，英国的衡平法诞生之初也有类似的特点：如果严格遵循先例无法获得公平的结果，那就绕过普通法，按照法官自由心证中的公平概念来判案。美国的法律和英国一脉相承，衡平法在美国同样被大量适用，宪法3.2款为这样的适用提供明确的保障。
This is also what makes contract law one of the easiest among the eight MBE subjects: the questions will not allow grossly unfair outcomes to occur. If the common law cannot achieve complete fairness, we use equity to bridge the gap. Chinese bar examinees often joke that solving civil law questions relies entirely on basic moral values, and the same holds true for U.S. contract law.
这也是让合同法成为了8个部门法中最简单的一门：题目不会允许特别不公平的事情发生。普通法如果做不到十分公平，我们就用衡平法来弥补。中国的法考考生经常调侃做民法题完全凭借朴素的价值观，美国的合同法也同样如此。
Example: A agrees to pay B $100,000 to build a house. B spends $80,000 on materials alone and another $40,000 on labor before running out of money and abandoning the project. A then hires C, who finishes the house for only $40,000. The completed house is worth $200,000. How much can B recover if he sues A? It is difficult to solve this using the theories we learned earlier because B did not achieve "substantial performance" and is in breach, meaning A has no obligation to pay. However, applying basic moral values, A originally intended to spend $100,000 to build the house but ended up spending only $40,000. Therefore, A should pay B $60,000 to prevent unjust enrichment. In equity, this $60,000 is called restitution.
甲约定支付乙10万建造房屋，乙光买材料就花了8万，又花了4万人工后入不敷出，于是放弃。甲于是找到丙，只支付4万就盖好了房子，房子盖好后价值20万，问乙起诉甲可以被法院支持多少。我们很难用前面学过的理论来做这个题，因为这里乙没有达到“实质履行”，构成违约，这样甲就没有付款义务。但我们用朴素的价值观来考虑，甲本来要花10万建造房屋，结果只花了4万，所以甲应该支付给乙6万来避免不当得利（unjust enrichment）。这6万在衡平法中叫做不当得利的返还（restitution）。
Today, equity has developed its own unique set of rules. We will outline some broad principles here and reinforce them later in the Constitutional Law and Civil Procedure sections:
时至今日，衡平法自己也形成了一套独特的规则，我们先把一些大原则说在这里，到宪法和民诉阶段我们还会再强化：
Example: Although restitution deals with money, it is still an equitable remedy; its essence is to "restore" unjust enrichment rather than to "compensate" for a loss.
不当得利的返还（restitution）虽然关注的是金钱，但依然是衡平法救济，它本质上是“返还”不当得利，而不是“赔偿”损失。
Example: Demanding back pay for past pensions is a common law remedy, but demanding the continued payment of pensions every month in the future is an equitable remedy.
要求补发过去的养老金是普通法救济，要求未来每个月都继续发放养老金却是衡平法救济。
Example: MBE questions often present both common law (or UCC) and equitable options simultaneously. We must focus on whether a contract was formed. If a contract exists, issues are generally resolved using the aforementioned damages rules unless it causes manifest injustice. Equitable theories, such as quasi-contract or estoppel, are typically used only when no contract was formed.
题目中经常会同时出现普通法（UCC）和衡平法选项，我们要关注合同是否成立，如果合同成立，一般来说按照前面的赔偿金解决问题，除非造成明显的不公。只有当合同没有成立时才用衡平法理论解决问题，比如准合同、禁反言等。
Example: A seller agrees to sell a parcel of land. The buyer breaches but is willing to pay the price difference, and the seller can easily sell the land to a third party. The seller cannot force the buyer to purchase the land (specific performance) because monetary damages provide an adequate remedy.
卖家出售一块地，买家违约，并愿意赔偿差价，卖家也能够很容易将地卖给第三方。卖家无法强制要求买家将地买走，因为金钱赔偿是足够的救济。
Example: A buyer agrees to purchase a parcel of land. The seller breaches but is willing to pay the price difference. For the buyer, every parcel of land is unique, so they can most likely demand specific performance to obtain the land (an equitable remedy). Of course, the buyer can also opt for common law damages.
买家购买一块地，卖家违约，并愿意赔偿差价。对于买家来说，每一块地都是不相同的，大概率可以要求强制过户获得土地（衡平法救济）。当然，买家也可以选择普通法赔偿。
Example: A agrees to pay B $200,000 to build a house. B's expected cost is $160,000. When the construction is 75% complete, B stops work without cause. A hires C, who has special building skills and finishes the house for only an additional $20,000. We should not require A to return $180,000 in unjust enrichment as in the previous example, because compared to the non-breaching party being unjustly enriched, we are even more reluctant to see the breaching party unjustly enriched. The court may require A to pay 75% of the contract price, which is $150,000; or it may require A to pay 75% of B's cost, which is $120,000.
甲约定支付乙20万建造房屋，乙需要花费的成本为16万，建造到75%时乙无故停工。甲找到丙，丙有特别的建房技巧，只额外花了2万就造好了房屋。我们不应该像上例那样要求甲退回不当得利18万，因为相比守约方的不当得利，我们更不希望看到违约方不当得利。法院可以要求甲支付合同价的75%，即15万；也可以要求支付乙成本价的75%，即12万。
Finally, many concepts exist in both common law and equity, such as estoppel, and even quasi-contract is a common law concept based on equitable principles. I group them under equity to help you understand the equitable mindset. I will emphasize when a clear distinction between common law and equity is necessary.
最后，很多概念在普通法和衡平法概念都有，比如禁反言（estoppel），甚至准合同（quasi-contract）是基于衡平法理念的普通法概念。我统一放在衡平法下面讲，是为了让大家了解衡平法的思路。需要明确区分普通法和衡平法时我会强调。
禁反言Estoppel
We have previously discussed in many places that if a party makes a promise and the other party has made arrangements to their detriment based on reliance (detrimental reliance), the promisor may not renege. For example:
我们此前在很多地方讲过如果一方作出承诺，对方已经基于信赖作出有损害的安排（detrimental reliance），则承诺方不得反悔。比如：
After an option contract is rejected, it remains valid until expiration (the offeree can change their mind), unless the offeror has taken subsequent action in reliance on the rejection.
Option Contract被拒绝后，到期之前依然有效（可以反悔），除非提出人基于对拒绝的信赖作出了后续行为。
If an acceptance is mailed first and a rejection is mailed later, the contract is formed when the acceptance is mailed. This is unless the offeror receives the rejection letter first and makes subsequent arrangements in reliance on the rejection.
先寄出同意要约，后寄出拒绝要约，则前一个寄出时合同已经成立。除非提出要约的人先收到了拒绝要约的信，并基于对拒绝的信赖作出后续安排。
This principle is called estoppel, and it is universally applicable in contract law. If a contract is not formed according to the principles we discussed earlier, is unenforceable, or even if a party breaches, but the promisee has made arrangements in reliance on the promise, you need to consider the principle of estoppel when answering questions.
这个原则叫禁反言（estoppel），在合同法中普遍有效。如果根据我们前面说的原则合同没有成立，合同无法执行，甚至一方违约，但如果被承诺方基于对承诺的信赖作出了安排，做题时需要考虑禁反言原则。
A tells B, "If you come to my house, I will give you an antique." B spends thousands of dollars to fly business class to A's house. Although there is no consideration and the promise to give the antique is unenforceable, B can demand that A compensate for the thousands of dollars in airfare.
甲对乙说，你要来我家，我就送你一件古董。乙花费数千美元，搭乘商务舱来到甲家里。虽然没有对价，无法执行古董，但可以要求甲赔偿数千美元的机票费用。
A promises to gift B 1 million. Based on this, B buys a car for 100,000. Although the gift contract is unenforceable due to lack of consideration, B can claim the 100,000 spent in reliance on the promised gift.
甲承诺赠与乙100万，乙基于此买了一辆10万的车。虽然赠与合同因为没有对价无法执行，但乙可以主张基于受赠与的信赖花的10万元。
A and B orally agree that A will buy B's used car for $50,000, provided that B refurbishes the car. B spends $5,000 to refurbish the car, but A asserts the Statute of Frauds to render the contract unenforceable. Although the contract will not become enforceable because of the arrangements B made, B can claim the $5,000 refurbishment cost.
甲乙口头约定乙5万美元交易乙的二手车，前提是乙去将二手车翻新，乙花了5000美元翻新二手车，甲却主张反欺诈法导致合同无法执行。虽然合同不会因为乙作出的安排变得可以执行，但乙可以主张5000美元的翻新费用。
The arrangement made in reliance must be detrimental.
基于信赖作出的安排必须是有损害的（detrimental）。
A promises to gift B 10,000. Based on this, B books a luxury suite for 10,000 a night, which can be canceled at any time. A feels B is too extravagant and refuses the gift. Although B made arrangements, B can cancel the reservation without any loss, and the contract remains unenforceable due to lack of consideration.
甲承诺赠与乙1万元，乙基于此订了一晚1万元的豪华套间，可以随时取消。甲觉得乙太过挥霍，于是拒绝赠与。虽然乙作出了安排，但乙可以取消预订，没有任何损失，合同依然因为没有对价而无法执行。
We also use the estoppel theory to resolve issues of breach by the general contractor or subcontractor in bidding, and it can even make a contract formed that would otherwise not be formed under common law.
我们还用禁反言理论来解决竞标中发包方或承包方违约的问题，甚至可以让原本普通法下不成立的合同变得成立了。
A general contractor asks a subcontractor for a quote on a project. The subcontractor quotes 1 billion. The general contractor calculates its own costs and wins the bid at 1.1 billion. Later, the subcontractor revokes the quote, and the general contractor finds a third party to complete the project for 1.2 billion. The subcontractor could reasonably foresee that the general contractor would bid in reliance on its quote, so it must bear the loss.
承包方询问分包方一个工程的报价，分包方报价10亿，承包方计算自己的成本后以11亿的价格中标，后分包方撤回报价，承包方以12亿的价格找第三方完成工程。分包方能够合理预见到承包方会基于对自己的报价的信赖投标，所以需要承担损失。
In the above example, the subcontractor should reasonably foresee that the general contractor would make arrangements in reliance on the offer. Even if the general contractor accepts the offer after it is revoked, the contract can still be considered formed, and expectation damages can be claimed. This is a supplement using equity theory to the rule that "a common law offer without consideration can be revoked at any time".
在上例中，分包方应当合理预见到承包商会基于对offer的信赖作出安排。即使承包方在offer撤回之后接受了offer，依然可以认为合同成立，主张期望赔偿金。这是用衡平法理论对“没有对价的普通法offer可以随时撤销”的补充。
不当得利Unjust Enrichment
Unjust enrichment is an important principle of equity, meaning to unjustly benefit at the expense of another person. We have previously introduced the application of restitution.
不当得利（unjust enrichment）是衡平法重要原则，即不公正地以牺牲另一个人的利益为代价而获利。前面我们已经介绍了不当得利返还（restitution）的适用。
A quasi-contract (implied-in-law contract) is when a contract is not legally formed or is unenforceable, but one party has partially or fully performed and the other party is unjustly enriched, the court may construct and enforce a contract.
准合同（quasi-contract, implied in law contract）是在合同依法不成立、无法执行时，但一方已经部分或全部履行、另外一方不当得利时，法院可以拟制一个合同并执行。
A doctor sees a patient fainted on the side of the road and revives him. Although there is no mutual assent to form a contract, the court can require the patient to pay the doctor appropriate medical fees based on the quasi-contract theory.
医生看到昏倒在路边的病人后把他救醒，虽然没有合意无法形成合同，但法院可以基于准合同理论让病人支付给医生适当的医疗费用。
We must distinguish between a quasi-contract and an implied-in-fact contract. An implied-in-fact contract refers to a situation where there is no verbal communication between the parties, but a contract is formed in fact, similar to the "implied acceptance of an offer" mentioned earlier.
我们要将准合同和事实合同（implied in fact contract）区分开来，事实合同是指双方没有言语的交流，但合同事实上成立，类似前文的“默示接受要约”。
A drives a car to the gas pump, and the attendant fills up the tank. Although there is no verbal communication between the two parties, a contract is formed in fact.
甲将车开到油枪边，服务员把油加满，虽然双方没有任何言语交流，但合同事实上成立。
特殊履行Specific Performance
Specific performance is a method of performance other than the payment of money. Usually, only when the subject matter of the transaction is very unique and cannot be measured by money, or when monetary damages are clearly inadequate, the court may order specific performance. It should be noted that the Constitution prohibits involuntary servitude, so courts almost never order a defendant to be forced to provide services to a plaintiff.
特殊履行（specific performance）即给付金钱以外的履行方式，通常只有当交易的物品非常特殊无法用金钱衡量时，或者用金钱给付救济明显效率不高时，法院可以决定判特殊履行。需要注意的是，宪法禁止强制劳役，所以法院几乎从来不判让被告强制给原告提供服务。
A is a world-famous painter. B pays A to paint a picture of "A Painted-Face Monkey Bathing". A gladly accepts, but later breaches the contract. Although monetary damages are insufficient to compensate for B's loss, the court will not force A to create the painting.
甲是世界出名的画家，乙支付甲要求画一幅《花脸猴出浴图》，甲欣然接受，后甲违约。虽然金钱给付救济不足以弥补乙的损失，但法院也不会强制让甲创作。
A court can order someone to demolish an illegally built addition to a house; if they do not demolish it themselves, the court will hire someone to demolish it for them.
法院可以要求某人必须拆除非法加盖的房屋，如果自己不拆，法院就请人帮他来拆。
In an antique transaction where the antique dealer breaches, the court may order the dealer to deliver the specific antique to the buyer (replevin).
在古董交易中古董商违约，法院可能会判古董商把特定的古董交付给买家（replevin）。
If a seller hears news that the buyer is about to go bankrupt right after shipping the goods, the seller can exercise the right of reclamation to directly reclaim the goods. The buyer also has the right to demand replevin under specific circumstances. Although replevin looks very much like "making someone do something," it happens to be a common law remedy.
卖家刚发货就听到买家即将破产的消息，卖家可以行使破产取回权（reclamation）直接取回货物。买家在特定情况下也有要求返还原物（replevin）的权利。返还原物虽然看起来很像是“让做某事”，但偏偏是普通法救济。
In the previous two examples, we see that replevin (reclaiming items, returning the original property) can be part of a final judgment or applied for during the litigation.
在前面两个例子中，我们看到replevin（取回物品、返还原物）可以是最终判决的一部分，也可以在诉中申请。
Relief applied for during litigation is generally equitable, such as a preliminary injunction and a temporary restraining order, which we will explain in detail in the Civil Procedure section.
诉中申请的救济一般都是衡平法，比如初步禁令（preliminary injunction）和临时禁止令（temporary restraining order），我们会在民诉篇详细讲解。
Considering that involuntary servitude cannot be forced, apart from replevin, specific performance in exam questions is mostly related to the forced transfer of real estate, stocks, etc. We have already introduced the difference between buyers and sellers demanding specific performance earlier.
考虑到并不能强制劳役，所以除了返还原物（replevin），考题中的特殊履行大部分时候和房地产、股票等的强制过户有关，我们已经在前面介绍了买家和卖家要求强制履行的区别。
Although an individual cannot be forced to do something, the government can be forced to do something, such as being required to issue a marriage license to a same-sex couple, which we will study in detail in the Constitutional Law section.
虽然不能强制个人做某事，却可以强制要求政府做某事，比如必须给一对同性恋发放结婚证，我们会在宪法篇详细学习。
解除合同和重写合同Rescission and Reformation
Rescission is the remedy taken by a party when a contract is voidable, as we discussed earlier. Examples include mutual mistake, fraud, undue influence, etc.
解除合同（rescission）是我们前面所说当合同可撤销时一方采取的救济。比如共同误解、欺诈、不当影响等。
Reformation is the remedy taken when a contract does not reflect the parties' intent due to a clerical error, as we discussed earlier, and it also includes a mutual mistake in integration when the parties translate an oral agreement into a written contract, or a unilateral mistake plus fraud.
重写合同（reformation）是我们前面所说当合同因为书记错误（clerical error）导致和双方的意思不符时采取的救济，也包括双方在将口头协议转化为书面合同时发生的共同错误（mutual mistake in integration），或者一方错误加上另一方的欺诈（unilateral mistake + fraud）。
Both rescission and reformation are equitable remedies, and equitable defenses can be raised against these claims. In addition, if a bona fide purchaser has acquired the subject matter, this can be used as a defense against reformation.
解除合同和重写合同都是衡平法救济，对于这两个主张可以采取衡平法抗辩。此外，善意第三人（bona fide purchaser）如果取得了标的物，可以用来对抗合同的重写。
衡平法抗辩Equitable Defenses
If the plaintiff asserts an equitable claim, the defendant may raise equitable defenses.
如果原告提出衡平法的主张，被告可以提出衡平法抗辩。
Laches refers to the plaintiff's unreasonable delay in asserting their rights. Unlike the statute of limitations, laches does not have a specific timetable. If the plaintiff has long known of their rights but intentionally waits until the cost of performance increases or performance becomes disadvantageous to the defendant before exercising them, the court may reduce or deny the plaintiff's claim.
懈怠（laches）是指原告怠于行使自己的权利。和诉讼时效（statute of limitation）不同的是，懈怠没有明确的时间表。如果原告早就知道自己的权益，但故意等到履行成本增加或者履行对被告不利是才行使，法院可能会调低原告主张的请求。
Example: A buyer purchases a house, but the seller delays the transaction, and the buyer does not urge them. A year later, the house price has appreciated by 50%, and the buyer demands specific performance (an equitable remedy). The seller can raise laches as a defense, arguing that the buyer is also responsible for the delay. A smarter approach would be to claim common law damages within the statute of limitations, so the seller cannot raise equitable defenses.
买家购买一套房屋，但卖家迟迟不交易，买家也并不催。一年之后，房价升值了50%，买家要求强制过户（衡平法救济）。卖家可以用懈怠为由抗辩，主张买家同样也有责任。比较聪明的做法是在诉讼时效内提出普通法赔偿，这样卖家就无法提出衡平法抗辩。
Unclean hands means that the plaintiff is also at fault or has acted unethically with respect to the matter at hand.
脏手（unclean hands）是指原告对事情的发生也有过错。
Hardship means that specific performance would impose a massive and unfair burden on the defendant that is disproportionate to the plaintiff's benefit.
困难（hardship）是指强制履行会给被告带来与原告收益不成比例的巨大且不公平的负担。
A purchases a parcel of land from B. After contracting, due to a sudden natural disaster, B's only residence is destroyed, and B has to move into an old house on that land. B refuses to transfer the title. We learned earlier that this contract is formed and enforceable, but if A demands specific performance to force the transfer of the land (an equitable remedy), B might raise the defense of hardship, arguing that forced transfer would cause B extreme survival difficulties, far exceeding A's loss from not obtaining the land.
甲向乙购买一块土地。签约后，由于突发的自然灾害，乙的唯一住所被毁，只能搬到该土地上的旧屋居住。乙拒绝过户。我们之前学过该合同成立并且可以执行，但如果甲要求特殊履行强制过户土地（衡平法救济），乙或许可以提出困难抗辩（Hardship），主张强制过户会给乙造成极大的生存困难，且远超甲未获得土地的损失。
Estoppel means that the plaintiff has caused the defendant to reasonably rely on the premise that the plaintiff will no longer assert the claim, and the defendant has changed their position based on that reliance.
禁反言（estoppel）是指原告已经让被告合理信赖原告不会再主张该诉讼请求，且被告基于该信赖已经作出安排。
Mitigation of damages means that if the plaintiff could have promptly reduced their losses but failed to act, the defendant can ask the court to hold the plaintiff responsible for the losses that could have been avoided. It should be noted that mitigation of damages is a limitation rule on damages under common law and does not belong to equitable defenses.
减少损失（mitigation of damages）是指如果原告明明可以及时减少损失却没有行动，被告可以要求法院让原告承担原本可以减少的损失。需要注意的是，减少损失属于普通法上的损害赔偿限制规则，不属于衡平法抗辩。
Equitable defenses may not necessarily invalidate the plaintiff's claim entirely, but they might reduce the plaintiff's recovery or limit the remedies granted.
衡平法抗辩不一定能完全让原告的主张完全失效，但或许可以让原告的主张打折扣。