The parties to a contract of sale are called the seller and the buyer. The Sale of Goods Act (Ont. s. 2; U.K. s. 62) defines the former as meaning a person who sells or agrees to sell goods, and the latter as a person who buys or agrees to buy goods.
The Sale of Goods Act (Ont. s. 4; U. K. s. 2) provides:
4. - (1) Capacity to buy and sell is regulated by the general law concerning capacity to contract, and to transfer and acquire property.
(The rest of the section relates to necessaries - a subject which is discussed in 13).
(1) Lunatics and drunken persons.
The general rule as to the contract of a lunatic (at all events if not so found by inquisition), or drunken man, who by reason of lunacy or drunkenness is not capable of understanding its terms or forming a rational judgment of its effect on his interests, is that such a contract is voidable at his option, but only if his state is known to the other party. The defendant who sets up his own incapacity as a defence must prove not only that incapacity but the plaintiff's knowledge of it at the date of the contract.
Pollock, Contract, 8th ed., 1911, p. 97; Molton v. Cam-roux, 1849, 4 Ex. 17, 6 R.C. 71; Matthews v. Baxter, 1873, L.R. 8 Ex. 132; Imperial Loan Co. v. Stone,  1 Q.B. 599; Robertson v. Kelly, 1882, 2 O.R, 163; Murray v. Weiler, 1910, 3 Alta. L.R. 180; Bawlf Grain Co. v. Ross, 1917, 55 CanS.C.R. 232, 37 D.L.R. 620, reversing 11 Alta. L.R26; Conrad v. Halifax Lumber Co., 1918, 52 N.S.R. 250, 41 D.L.R. 218.
An infant is not absolutely incapable of binding himself, but is, generally speaking, incapable of absolutely binding himself by contract. His acts and contracts are voidable at his option, subject to certain statutory and other exceptions.
Pollock, Contract, 8th ed., 1911, p. 56; see also Bruce v.
Warwick, 1815, 2 M. & S. 205, 6 Taunt. 118, 6 Rc. 43;
Cowern v. Nield,  2 K.B. 419 (infant not liable for the price of goods sold and delivered) ; Stocks v. Wilson,  2 K.B. 235; Leslie v. Shiell,  3 K.B. 606 (misrepresentation of age).
In Ontario it is provided by the Statute of Frauds, R.S.O., 1914, c. 102, s. 7 (re-enacting Lord Tenterden's Act, 9 G. 4, c. 14, s. 5), as follows:
7. No action shall be maintained whereby to charge any person upon any promise made after full age to pay any debt contracted during infancy, or upon any ratification after full age of any promise or simple contract made during infancy, unless the promise or ratification is made by some writing signed by the party to be charged therewith or by his agent duly authorized to make the promise or ratification.
In the United Kingdom Lord Tenterden's Act has been superseded by the Infants' Relief Act, 1874, which provides as follows:
1. All contracts, whether by specialty or by simple contract, henceforth entered into by infants for the repayment of money lent or to be lent, or for goods supplied or to be supplied (other than contracts for necessaries), and all accounts stated with infants, shall be absolutely void: Provided always, that this enactment shall not invalidate any contract into which an infant may, by any existing or future statute, or by the rules of common law or equity, enter, except such as now by law are voidable.
2. No action shall be brought whereby to charge any person upon any promise made after full age to pay any debt contracted during infancy, or upon any ratification made after full age of any promise or contract made during infancy, whether there shall or shall not be any new-consideration for such promise or ratification after full age.
12. Parties And Their Capacity.
Both under Lord Tenterden's Act and under the Infants' Relief Act a distinction must be made between a contract which is not binding upon an infant unless he ratifies it after attaining his majority, and a contract which is binding on him unless he repudiates it within a reasonable period after attaining his majority. If a contract is of a continuing character, or if under a contract an infant acquires an interest in permanent property to which obligations attach, as, for instance, shares in a company, he must, in order to avoid the obligations, repudiate the contract and disclaim the property, if any, within a reasonable period after coming of age. As no ratification is required in such a case, the statutes in question do not apply.
Edwards v. Carter,  A.C. 360, affirming Carter v. Silber,  2 Ch. 278; Carnell v. Harrison,  1 Ch. 328; cf. notes to Bruce v. Warwick, in 6 R.C. 50 ff.; Millson v. Smale, 1894, 25 O.R. 144; Re Sovereign Bank, Clark's Case, 1916, 35 0. L.R. 448, 27 D.L.R. 253.
But in the case of contracts by infants to do isolated or single acts, as, for instance, a contract for the sale of goods, a ratification by the infant after coming of age was necessary at common law to render him liable. Under the Infants' Relief Act, 1874, such a ratification is now void, even though made on new consideration, and under Lord Tenterden's Act ratification is unenforceable unless it is in writing.
Smith v. King,  2 Q.B. 543; Louden Mfg. Co. v. Milmine, 1907, 15 O.L.R. 53 ; Great West Implement Co. v. Grams, 1908. 1 Alta. L.R. 411.
A person may, however, render himself liable upon a new promise made after attaining his majority, as distinguished from the ratification after attaining his majority of a promise made during his infancy.
Ditcham v. Worrall, 1880, 5 Crd. 410; Smith v. Jamieson, 1889, 17 O.R. 626.