Before a final summary is attempted it should be observed that it is not essential in order that a promise shall be sufficient consideration that its performance will certainly prove detrimental to the promisor or beneficial to the promisee. A conditional promise is sufficient consideration. The performance of such a promise does not necessarily involve either detriment or benefit, since the condition upon which any action of the promisor is to take place may not happen. But the possibility that the condition may happen, involves a chance of detriment which is sufficient to make the promise valid consideration.74 Even though the condition in a promise relates to an unknown fact which is already determined so that if the parties knew the truth it would be apparent that the promisor really bound himself for nothing the consideration is sufficient.75

71 "A promise is a good consideration for a promise. But no promise constitutes a consideration which is not obligatory upon the party promising," per Sanborn, J. Coldblaat Transportation Co. v. Kansas City Bolt & Nut Co., 114 Fed. 77, 52 C. C. A. 25, 57 L. R. A. 696. A contract must be obligatory upon both parties so that each may have an action upon it. Mc-Gowin etc Co. v. R. J. & B. F. Camp Lumber Co., 192 Ala. 35, 68 So. 263, 264.

72 "Either all is a nudum pactum or else the one promise is as good as the other." Harrison v. Cage, 5 Mod. 4118, per Holt, C. J.: "The promises must be concurrent and obligatory upon each at the same time to render either binding." Morrow v. Southern Express Co., 101 Ga. 810, 28 S. E. 008; Simpson v. Sanders, 130 Ga. 265,268,60 S. E. 541; Reding v. Anderson, 72 Ia. 498, 34 N. W. 300; Citizens' Nat. Life Ins. Co. v. Murphy, 154 Ky. 88, 156 S. W. 1069; El Paso, etc., R. Co. v. Eichel (Tex. Civ. App.), 130 S. W. 922.

73See criticism of this terminology, infra, Sec. 140.

The result of this argument is that no briefer definition of sufficient consideration in a bilateral contract can be given than this: Mutual promises in each of which the promisor undertakes some act or forbearance that will be, or apparently may be, detrimental to the promisor or beneficial to the promisee, and neither of which is rendered void by any rule of law other than that relating to consideration, are sufficient consideration for one another.

Cases where a promisor warrants the truth of existing facts have been put in opposition to the argument that a promise must in order to furnish sufficient consideration be a promise of something which would if actually given be sufficient consideration for a unilateral contract. It is said:

"I agree that a horse which I sell shall be sound, or shall win a race; or that a man shall pay his debts; or that a ship shall come safe to port: in all these cases my promise is a valid consideration for a counter-promise. Yet the soundness or speed of the horse, the solvency of the third party, or the safety of the ship could not be a valid consideration for a promise made to me." 76 Here, there is no inconsistency or exception. A warranty or promise of the truth of an existing fact can only be understood as meaning a promise to be responsible in damages if the fact asserted is not true. The warranty of the existence of an event in the future when construed means either a promise to bring about the existence of the event or a promise to pay damages if the event does not happen,77 and either the present causation of the fact or the present payment of damages for the unsoundness or lack of speed of the horse, the insolvency of the third party, or the loss of the ship would be as sufficient consideration as the promise of warranty.

74 See infra, Sec. 112. Where under the law three of the thirteen saloons in a town would be compelled to go out of business, and the saloon keepers agree that three of them, including plaintiff, should be given 3400 each to retire, there was a valuable consideration for the promise to pay. Janes v. Mass, 78 Wash. 517, 136 Pac. 680.

75See infra, Sec. 119.

76 Professor Beale, 17 Harv. L. Rev. 82.