Since, then, it cannot be admitted that mutual promises are always sufficient consideration for one another, it becomes necessary to determine in what cases a promise is a sufficient consideration for a counter-promise. Two tests have been suggested either explicitly or implicitly:
1. Sir Frederick Pollock and Professor Langdell apply this test: If the obligation of a promise would be a detriment to the promisor (assuming that the promise creates a binding obligation) the promise is sufficient consideration.
2. "That most accurate of writers, Mr. Stephen Leake," 53 whose work on contracts has long been a standard treatise, says, however,-
"So far as regards the matter of the consideration, as being executed or executory, it may be observed that whatever matter, if executed, is sufficient to form a good executed consideration; if promised, is sufficient to form a good executory consideration: so that the distinction of executed and executory consideration has no bearing upon the question of the sufficiency of any particular matter to form a consideration." 54
The second of the views thus stated seems to be that sanctioned by the law, and, moreover, intrinsically is the more reasonable of the two. When bilateral contracts were first recognized no elaborate discussion was had of the requirements of a promise which might be sufficient consideration for another promise. It was simply decided that a promise was sufficient consideration for another promise. It was not long, however, before some definition was made of the character of a promise which would be sufficient consideration for another promise. Lord Holt stated that "where the doing a thing will be a good consideration, a promise to do that thing will be so too." 55 In subsequent cases there has been very little attempt at exact definition, but the notorious failure of the courts to mark the distinction between unilateral and bilateral contracts until recently (of which the failure to provide any brief name to distinguish the two is an indication), shows that the court must have applied to bilateral contracts a test which would be just as applicable had the contract been unilateral, and an examination of the cases shows that even where it plainly appears that the contract was bilateral, the court in discussing the sufficiency of consideration, considered the character of the things promised.56
53 2 Taw Quarterly Rev. 113.
54 Leake on Contracts (1st ed.),page 314; (2d ed.), pp. 612, 613. In the third edition the author states in his preface that finding the book "has been more used in the practice of the profession than in the study of the law, for which as originally prepared, he thought it might perhaps be useful . . . he has endeavored to revise the work strictly for the service of the profession with the single aim of presenting a convenient digest of the leading principles of the law of contracts as derived from judicial exposition." The author, with this aim in view, considerably diminished the size of the book, and the passage, above quoted, was omitted.
But occasionally a court has made a statement in clear terms. Lord Blackburn, than whom no better modern authority could be cited, stated the principle as follows:
55Thorp v. Thorp, 13 Mod. 465, (1701).
56 In Thomas v. Thomas, 2 Q. B. 851, there was plainly set out a written agreement containing mutual promises. The court in considering the sufficiency of consideration examined the nature of the things promised. Thus Lord Denman said: "Then the obligation to repair is one which might impose charges heavier than the value of the life estate." So Patteson, J., in speaking of the sufficiency of the plaintiffs promise, expressly considers the sufficiency of the things promised by her; namely, payment of rent and making of repairs. Such statements as that made in Benson v. Phipps, 87 Tex. 578, 29 S. W. 1061, 47 Am. St. Rep. 128, "a promise to do what one is not bound to do, or to forbear what one is not bound to forbear, is a good consideration for a contract," necessarily involve the assumption that no promise is sufficient consideration unless the thing promised would be. In Morrow v. Southern Express Co., 101 Ga. 810, 28 S. E. 998, and Simpson v. Sanders, 130 Ga. 265, 268, 60 S. E. 541, the court said: "If one assumes under such an agreement [by mutual promisee] to do a special act beneficial to another, and that other under the terms of the contract is under no obligation to perform an act of corresponding advantage to the former, the agreement is without such consideration as will support the promise of the party assuming to perform." In Schuler v. Myton, 48 Kans. 282, 29 Pac. 163, the court said: "It is well settled that an agreement to do or the doing of which one is already bound to do does not constitute a consideration for a new promise." Similarly in Cobb v. Cow-dery, 40 Vt. 25, 28, 94 Am. Dec. 370, the court said: "And so it would be in any other case where the only consideration for the promise of one party was the promise of the other party to do, or his actual doing, something which he was previously bound in law to do." See also Robinson v. Jewett, 116 N. Y. 40, 22 N. E. 224, where in dealing with a written contract containing mutual promises and signed by both parties the court (at page 53) discuses the insufficiency of certain acts promised to serve as consideration.
"The general rule is, that as executory agreement by which the plaintiff agrees to do something on the terms that the defendant agrees to do something else, may be enforced, if what the plaintiff has agreed to do is 'either for the benefit of the defendant or to the trouble or prejudice of the plaintiff.' " 57 The Minnesota court has made an equally plain statement:
"The case is, then, one of a promise on the part of the plaintiff to do something of advantage in law to the defendant, and on the part of the defendant to do something of advantage in law to the plaintiff-a case of mutual promises, one of which is the consideration of the other. The agreement was valid and binding upon both parties." 58
The elaborate definition given in Currie v. Misa,59 "A valuable consideration in the sense of the law may 'consist either in some right, interest, profit, or benefit accruing to one party, or some forbearance, detriment, loss, or responsibility given, suffered, or undertaken by the other," contains in substance the same principle.60
The definitions of modern American text writers often state clearly the same test.61