b. Benefit and detriment. Historically, the common law action of debt was said to require a quid pro quo, and that requirement may have led to statements that consideration must be a benefit to the promisor. But contracts were enforced in the common-law action of assumpsit without any such requirement; in actions of assumpsit the emphasis was rather on the harm to the promisee, and detrimental reliance on a promise may still be the basis of contractual relief. See § 90. But reliance is not essential to the formation of a bargain, and remedies for breach have long been given in cases of exchange of promise for promise where neither party has begun to perform. Today when it is said that consideration must involve a detriment to the promisee, the supposed requirement is often qualified by a statement that a "legal detriment" is sufficient even though there is no economic detriment or other actual loss. It is more realistic to say simply that there is no requirement of detriment.
　　b.收益和损害。从历史来看，普通法上的债的行为被认为要求一个等价物，而且这一要求还可能导出这样的结论：约因必须是允诺人获益。但在缺乏这一要求的契约在普通法上的违约之诉中仍然得到执行；在违约之诉中，强调的是对受允诺人的损害，而且对允诺的有害依赖可能仍然是契约救济的基础。参见第90条。但是信赖对协商的成立并非必要性因素，而且在任何一方当事人均未开始履行的允诺交换允诺的案例中，早已规定了违约救济。现在，当有人认为约因必须包括一个对于受允诺人的损害时，其假设的要求经常由此表述得以满足：“一个”法律上的损害”即使在没有经济损害或者其他实际损失的情况下仍然是充分的。认为没有对于损害的要求的主张是更加现实的。
　　Illustrations:　　
　　例释：
　　1. A contracts to sell property to B. As a favor to B, who is C''s friend, and in consideration of A''s performance of the contract, C guarantees that B will pay the agreed price. A''s performance is consideration for C''s promise. See § 73.
　　1.A通过订立契约向B出卖财产。作为B的朋友，出于好意并考虑到A对契约的履行，C担保B将给付议定的价格。A的履行是C的允诺的约因。参见第73条。

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