Bilateral and unilateral contracts;-bifactoral and unifactoral obligations.... 13 Executed and executory contracts... Void and voidable contracts.. § 1. Contract. 14 15 16 A contract is a promise, or set of promises, to which the law attaches legal obligation. This definition may seem somewhat unsatisfactory since it is necessary subsequently to define the circumstances under which the law does in fact attach legal obligation to promises, but in order to make a definition which should state these circumstances it would be necessary to compress the whole law of the formation of contracts into a sentence, which is impossible.' The definition given at least makes clear that the obligation of a contractor is based on a promise made by him.2 1 Many definitions of contract contain a reference to mutual assent and consideration, but these requirements are applicable only to simple contracts. 2 It has been suggested that the conception of a contract as necessarily involving a promise, is not accurate so far as formal contracts are con It is neither the circumstances which make a promise or set of promises binding nor the legal relations between the parties which arise from the existence of a binding promise or promises which constitute the contract, but the promise or promises themselves. Though language is often loosely used, blurring these distinctions, the meaning here adopted is that of customary legal usage and probably of scientific convenience also.3 § 2. Agreement. An agreement is an expression by two or more persons of assent in regard to some present or future performance by one or more of them.4 Agreement is in some respects a wider term than contract. It covers executed sales, gifts, and other transfers of property. It also covers promises to which the law attaches no legal obligation. An agreement is essential for the formation of a simple contract, but is not the only requisite. On the other hand, the common law recognized the possibility of contractual liability under a formal contract by the mere act of the obligor—that is, without agreement.5 cerned. Harriman on Contracts (2d ed.), § 623. It is doubtless true that the early conception of a sealed contract was analogous rather to a grant or to a conclusive statement of fact made in such fashion that the obligor could not dispute its correctness than to a promise, but in quite early times the validity of a covenant under seal in terms promising to do an act in the future was recognized, and it must have been very long ago when the conception of the meaning of such a covenant became substantially that which would be entertained to-day. At the present time even though a contract under seal be in the form of an acknowledgment of an existing indebtedness, it is clear enough that the language means in fact to the parties, as it means in law a promise. In defining what is a contract it must be remembered one is not explaining history, but analyzing the meaning of the word to-day. 3 "The act alone is the contract, the resulting contractual relation is quite a different thing." Holland, Jurisprudence (10th ed.), p. 251. Professor Corbin defines contract, it is true, as "the legal relations between persons arising from a voluntary expression of intention, and including at least one primary right in personam, actual or potential, with its corresponding duty," (26 Yale L. J. 170), but the terms of a contract do not necessarily include all the rights and duties which the law imposes when the contract is formed. See infra, § 615; and in any event the words contractual obligations and rights sufficiently express the relations between the parties. * See Carter v. Prairie Oil & Gas Co. 58 Okl. 365, 160 Pac. 319. See infra, § 205. § 3. Express and implied contracts; quasi-contracts. Contracts are express when their terms are stated by the parties. Contracts are implied when their terms are not so stated. The expression "implied contract" has given rise to great confusion in the law. Until recently the divisions of the law customarily made coincided with the forms of action known to the common law. Consequently, all rights enforced by the contractual actions of assumpsit, covenant and debt, were regarded as based on contracts. Some of these rights, however, were created not by any promise or mutual assent of the parties but were imposed by law on the defendant irrespective of, and sometimes in violation of, his intention. Such obligations were called implied contracts. A better name is that now generally in use of "quasi-contracts." This name is better since it makes clear that the obligations in question are not true contracts, and also because it avoids confusion with another class of obligations which have also been called implied contracts. This latter class consists of obligations arising from mutual agreement and intent to promise but where the agreement and promise have not been expressed in words. Such transactions are true contracts and have sometimes been called contracts implied in fact. In the present work the words implied contract will not be used to include quasi-contractual obligations. A "quasi-contract" is a constructive contract which is raised by law to enforce legal duties by contract actions, where an express or implied contract does not actually exist. Brown's Estate v. Stair, 25 Colo. App. 140, 136 Pac. 1003. 7A "contract implied in fact" requires a meeting of the minds, an agreement, just as much as an "express contract"; the difference between the two being largely in the character of the evidence by which they are established. Lombard v. Rahilly, 127 Minn. 449, 149 N. W. 950. In Highway Com'rs v. Bloomington, 253 III. 164, 97 N. E. 280, 284, in speaking of quasi-contracts, the Court said: "The liability exists from an implication of law that arises from the facts 6 and circumstances, independent of agreement or presumed intention. Pracht v. Daniels, 20 Colo. 100, 36 Pac. 845. In this class of cases, the notion of a contract is purely fictitious. There are none of the elements of a contract that are necessarily present. The intention of the parties in such case is entirely disregarded, while in cases of express and implied contracts in fact the intention is of the essence of the transaction. In the case of contracts, the parties fix their terms and set the bounds upon their liability. As has been said, in the case of contracts, the agreement defines the duty, while in the latter class of cases 'the duty defines the contract.' Hertzog v. Hertzog, 29 Pa. 465, 468; Columbus, Hocking Valley & Toledo Railway |