Contract

• 1. The Agreement Beneath Everything

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  A pharmaceutical company in nineteenth-century England advertised a smoke ball that, if sniffed three times daily for two weeks, would stop a user catching the flu. To prove its sincerity, the company said it had deposited £1,000 in the Alliance Bank, and promised £100 to anyone who used the ball and fell ill anyway. When a customer caught the flu and sued, the company called the advert a mere puff, not a serious offer.

  That dispute, Carlill v Carbolic Smoke Ball Co, sits inside something far larger than a quarrel over an influenza cure. It belongs to contract law, the branch of the law of obligations built on a single principle: that agreements must be honoured. A contract is an agreement specifying legally enforceable rights and obligations between two or more parties. Most often it involves consent to transfer goods, services, money, or a promise to do so later.

  But who decides whether a printed advertisement is a binding promise or empty boasting? Why does a peppercorn matter to a court? What separates a husband's broken promise to send his wife money from an agreement a judge will actually enforce? And why do contracts look so different depending on which country you happen to be standing in? Those questions run through everything that follows.

• 2. Two Great Traditions

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  Common law jurisdictions demand something extra before a simple agreement becomes binding: consideration, something of value given in exchange for a promise. Civil law and most mixed-law jurisdictions ask only for a meeting of the minds between the parties. That single divergence splits the legal world in two. Jurisdictions that were once British colonies generally adopted English common law. Others inherited or built civil law systems modelled on German or French codes.

  Within civil law there are sharply different families. The German tradition carries its unique doctrine of abstraction. Systems based on the Napoleonic Code draw systematic distinctions between different types of contracts. Roman-Dutch law rests on the writings of renaissance-era Dutch jurists and case law applying general principles of Roman law, from before the Netherlands adopted the Napoleonic Code.

  The map of these traditions was drawn by empire and revolution. Japan, South Korea, and the Republic of China modelled their contract law on the German pandectist tradition. The Arab world largely followed the Napoleonic Code. Dutch colonies kept Roman-Dutch law even after the Netherlands itself switched, which is why South Africa applies Roman-Dutch principles to private law while using English common law for most public law. Saint Lucia, Mauritius, Seychelles, and the Canadian province of Quebec became mixed-law jurisdictions leaning toward French tradition.

  In 1926, Turkey replaced its Ottoman-era blend of Islamic and secular law with a secular civil code modelled on Switzerland's, its contract and commercial law following the Swiss Code of Obligations. Following the Meiji Restoration, Japan adopted German-modelled codes and enacted its commercial code in 1899, spreading that system to Korea and China through occupation. In 1949, Abd El-Razzak El-Sanhuri and Edouard Lambert drafted the Egyptian Civil Code, modelled on the Napoleonic Code but fitted to Arab and Islamic society, and it became the template for most Arab states.

  In 2021, Mainland China adopted the Civil Code of the People's Republic of China, codifying contract law in book three. Its contract law draws on traditional Chinese views of law, the country's socialist background, the German-based law of Taiwan, and the English-based common law of Hong Kong, making it a de facto mixed system.

• 3. How a Promise Becomes Binding

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  In common law jurisdictions, forming a contract generally requires four things: an offer, an acceptance, consideration, and mutual intent to be bound. The parties must reach mutual assent, sometimes called a meeting of the minds. An offer is a promise dependent on a certain act, promise, or forbearance given in exchange. An acceptance that varies the offer's terms is not acceptance at all but a counteroffer, and therefore a rejection, under what lawyers call the mirror image rule.

  The objective approach to contractual intent was first used in the English case of Smith v Hughes in 1871. Intention is read from the perspective of a reasonable person, not from a party's private thoughts. The principle of offer and acceptance was later codified in the Indian Contract Act, 1872.

  Not every promise is a two-way street. A bilateral contract has each party making promises to the other; in a sale of a home, a buyer promises to pay the seller $200,000 in exchange for delivery of title. A unilateral contract is rarer, where one party promises but the other promises nothing. A person who loses a dog might publish a reward, and anyone who finds and returns the animal can claim it, yet no one is ever obliged to search. The High Court of Australia found the very label unilateral contract to be unscientific and misleading.

  Most advertisements that promise bargains are not offers at all. They are invitations to treat, a signal that a party is prepared to negotiate. In Pharmaceutical Society of Great Britain v Boots Cash Chemists, the court treated goods on a shelf this way. The smoke ball was the exception, because its specific promise of a reward read, to a reasonable man, as a serious offer rather than empty advertising.

• 4. The Peppercorn Problem

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  Consideration is the price for which the promise of the other is bought, in the words of Lord Dunedin in Dunlop v Selfridge. It can be a benefit to the promisor or a detriment to the promisee. Forbearance can count, but only if a legal right is actually surrendered. A simple contract needs it; a contract by deed does not. Under the Uniform Commercial Code, firm offers in most American jurisdictions are valid without it if signed by the offeror.

  The doctrine carries strict rules that have tripped up parties for two centuries. Consideration cannot be something that has already happened. In Eastwood v Kenyon in 1840, a guardian took out a loan to educate a young girl, and after her marriage her husband promised to repay it, but the court found the loan to be past consideration. Consideration cannot be a pre-existing duty either. In Stilk v Myrick in 1809, a captain promised to split two deserters' wages among the remaining crew if they sailed home short-handed, yet the promise failed because the crew were already contracted to sail.

  Value need not match value. A peppercorn describes consideration so small it is plainly inadequate, and yet it satisfies the law. That produces something the source compares to Hiyal in Islamic contracts, where parties meet a requirement technically while sidestepping its purpose. Critics call the whole doctrine a formality that complicates commerce and breeds legal uncertainty.

  The attack on consideration has teeth. The UNIDROIT Principles of International Commercial Contracts, published in 2016, reject it outright, arguing that eliminating it brings about greater certainty and reduces litigation in international trade. The United Nations Convention on Contracts for the International Sale of Goods also dispenses with it. Some commentators have proposed replacing consideration with estoppel as the basis for contracts.

• 5. When the Law Refuses to Listen

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  A husband once agreed to give his wife £30 a month while he was away from home, and when he stopped paying, the court refused to enforce the deal. That case, Balfour v Balfour, shows the law's reluctance to police domestic and social arrangements, which are presumed unenforceable on public policy grounds. The opposite happened in Merritt v Merritt, where an estranged couple's agreement was enforced because the circumstances showed they meant it to carry legal consequences.

  Commercial dealings flip the presumption. Parties are assumed to intend legal consequences unless they say otherwise. In Rose & Frank Co v JR Crompton & Bros Ltd, an honour clause declared the document not a commercial or legal agreement but only a statement of intention, and the court honoured that wish and declined to enforce it.

  Certain people are shielded from their own bargains. Very small children are not held to deals on the assumption they cannot understand them. Employees or directors who act ultra vires, beyond their power, may be barred from binding their company. People mentally incapacitated by disability or drunkenness may also lack capacity. Article 39 of the Philippine Civil Code lists the typical causes: age, mental disability, the state of being a deaf-mute, penalty, absence, insolvency, and trusteeship.

  The thresholds differ by place. In the United States, people under 18 are usually minors and their contracts are voidable, though benefits received must be returned if still returnable. In Singapore, minors are those under 21, yet sections 35 and 36 of the Civil Law Act 1909 treat certain contracts by those aged 18 and above as if made by adults. Under Singapore's Mental Capacity Act 2008, a person lacks capacity when an impairment of the mind or brain leaves them unable to make a decision, and a relative may obtain a lasting power of attorney over their welfare or finances.

• 6. Words, Conduct, And Silence

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  A person who signs a contractual document is bound by its terms, whether or not they have read it, under the rule in L'Estrange v Graucob, the signature rule. The High Court of Australia approved it in Toll (FGCT) Pty Ltd v Alphapharm Pty Ltd. Defences such as duress or unconscionability can still let a signer escape, and reasonable notice of the terms must be given before the contract is entered.

  Writing is not always required, but sometimes it is. In 1677, England passed the Statute of Frauds, which shaped similar laws in the United States and Australia. The Uniform Commercial Code generally requires a written contract for tangible product sales above $500 and for real estate. In the United Kingdom, the Law of Property Act 1925 keeps land deals in writing. Where the law does not demand writing, an oral contract, also called a parol or verbal contract, is generally valid and binding.

  Some terms are never spoken or written at all. Implied terms still form part of a contract, arising from the parties' conduct, from custom within an industry, or by operation of law. In the United Kingdom they may come from statute such as the Sale of Goods Act 1979 and the Consumer Rights Act 2015, from common law such as The Moorcock with its business efficacy test, from previous dealings as in Spurling v Bradshaw, or from custom as in Hutton v Warren.

  The weight of a term depends on what kind it is. English common law separates conditions from warranties: breaching a condition lets the other party repudiate and walk away, while breaching a warranty allows damages but not full discharge. The United Kingdom later developed the intermediate or innominate term, first established in Hong Kong Fir Shipping Co Ltd v Kawasaki Kisen Kaisha Ltd in 1962. In Bannerman v White, a buyer was allowed to reject hops treated with sulphur because he had stressed how much that mattered to him.

• 7. Breaking The Deal

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  An art collector buys a rare painting, and the seller refuses to hand it over. Money alone would be unjust here, so common law courts may order specific performance, compelling the contract to be carried out. The remedy is reserved for cases where damages fall short, and the sale of real property is the notable example, because land is treated as having unique value. In the United States, the 13th Amendment to the Constitution bars specific performance in personal service contracts except as punishment for a crime after conviction.

  Damages are the more common cure, and they come in several kinds. Compensatory damages aim to put the injured party in their rightful position, usually through expectation damages reflecting the bargain promised. Reliance damages cover expense incurred in reliance on a promise, awarded when profits are too speculative, as in the Australian case McRae v Commonwealth Disposals Commission over the right to salvage a ship. In Anglia Television Ltd v Reed, the English Court of Appeal awarded costs spent before the contract in preparing to perform.

  Limits guard against overreach. Liquidated damages are a loss agreed in advance, but penalty clauses serving a purely punitive purpose are void or limited on public policy grounds in most common and civil law jurisdictions. The test was established in Dunlop Pneumatic Tyre Co Ltd v New Garage & Motor Co Ltd. After a breach, the innocent party has a duty to mitigate loss, though Michael Furmston argued it is wrong to frame mitigation as a duty, citing The Solholt.

  Foreseeability draws the outer boundary of recovery. Hadley v Baxendale set the test: a loss must be foreseeable to the objective bystander or to parties with special knowledge. A miller lost production when a carrier delayed taking broken mill parts for repair, yet no damages were payable, because neither the reasonable man nor the carrier would have expected the miller to lack a spare part.

• 8. Grounds For Undoing

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  Caveat emptor, let the buyer beware, is the foundational principle applied to all American transactions. In Laidlaw v Organ, the Supreme Court held a buyer need not tell a seller information the buyer knew could affect the price. But that principle has limits, and the law recognises vitiating factors that can make a purported contract void or voidable.

  Misrepresentation is a false statement of fact made before a contract that induces a party to enter it. The remedy is rescission, and damages too if a tort is established. There are two types: fraud in the factum, which asks whether a party even knew they were making a contract, and fraud in inducement, which targets a misrepresentation that lured a party in. According to Gordon v Selico in 1986, misrepresentation can occur by words or conduct. Statements of opinion are generally not statements of fact, though in Bissett v Wilkinson a seller's claim that farmland would carry 2000 sheep was treated as opinion because the buyer was knowledgeable enough to judge it. In Singapore and the United Kingdom, the Misrepresentation Act 1967 lets even innocent misrepresentations ground damages.

  Mistake comes in three common law forms. Common mistake, where both parties share the same wrong belief, can only void a contract if the subject-matter was so fundamentally different as to make performance impossible, as in Bell v Lever Brothers Ltd and later Great Peace Shipping Ltd v Tsavliris Salvage. Mutual mistake, where each party means something different, is usually salvaged if a reasonable interpretation exists; see Raffles v Wichelhaus. Unilateral mistake, where only one party errs, is upheld unless the other knew and tried to exploit it, and a mistake about the other party's identity can void a contract, as Lord Denning held in Lewis v Avery.

  Pressure can undo a deal as well. The UNIDROIT Principles let a party avoid a contract concluded under another's unjustified threat that left no reasonable alternative, a concept common law calls duress. The same Principles allow a party to avoid a contract induced by fraudulent representation or by fraudulent non-disclosure of circumstances that fair dealing required to be disclosed. That international instrument keeps surfacing as the bridge between traditions, the same 2016 text that threw out both consideration and the German abstraction principle as ill-suited to modern business practice.