1 Williston on Contracts §112, p. 445 (3d ed. 1957)

1 WILLISTON ON CONTRACTS § 112, p. 445 (3d ed. 1957): "If a benevolent man says to a tramp: 'If you go around the corner to the clothing shop there, you may purchase an overcoat on my credit,’ noreasonable person would understand that the short walk was requested as the consideration for the promise, but that in the event of the tramp going to the shop the promisor would make him a gift. Yet the walk to the shop is in its nature capable of being consideration. It is a legal detriment to the tramp to make the walk, and the only reason why the walk is not consideration is because on a reasonable construction it must be held that the walk was not requested as the price of the promise, but was merely a condition of a gratuitous promise. It is often difficult to determine whether words of condition in a promise indicate a request for consideration or state a mere condition in a gratuitous promise. An aid, though not a conclusive test, in determining which construction of the promise is more reasonable is an inquiry whether the happening of the condition will be a benefit to the promisor. If so, it is a fair inference that the happening was requested as a consideration. On the other hand, if, as in the case of the tramp stated above, the happening of the condition will be not only of no benefit to the promisor but is obviously merely for the purpose of enabling the promisee to receive a gift, the happening of the event on which the promise is conditional, though brought about by the promisee in reliance on the promise, will not properly be construed as consideration. In case of doubt where the promisee has incurred a detriment on the faith of the promise, courts will naturally be loath to regard the promise as a mere gratuity and the detriment incurred as merely a condition. But in some cases it is so clear that a conditional gift was intended that even though the promisee has incurred detriment, the promise has been held unenforceable."