When we say there must be "consideration" in a contract we mean that neither party has a right to get anything from the other unless he has given or promised something in return. Various definitions of consideration are to be found in the text-books and judicial opinions. A sufficiently comprehensive one is: A benefit to the party promising, or a loss or detriment to the party to whom the promise is made. "Benefit" as thus employed, means that the promisor has, in return for his promise, acquired some legal right to which he would not otherwise have been entitled. And "detriment" means that the promisee has, in return for the promise, forborne some legal right which he otherwise would have been entitled to exercise. In all forms of contracts a consideration is absolutely necessary in order to enable either party to compel the other to do that to which they have agreed. In negotiable instruments, such as checks and drafts, the consideration is presumed to exist until it is proved that it does not. In most other forms of contracts the consideration need not appear on its face, but may be proved by parol or inferred from the terms of the agreement. Consideration can easily be understood if we view it as a price paid, without which the party receiving it would not have made the contract. Suppose A promises B $500 as a present and gives him a promissory note for that amount. B cannot make A pay him the $500, because there is no consideration for A's promise. But suppose B had given A his horse, worth $100, in exchange for A's promise to pay the $500. In that case A can be compelled to pay the $500, because there is consideration and it is not necessary that the consideration equal the promise in value. Frequently in business transactions of all kinds we find considerations of $1 paid, which will enable one to enforce agreements concerning even thousands of dollars. A past consideration or a moral obligation will not support a promise to do something. Thus, suppose A finds B's automobile, which has been stolen, and returns it to B. B promises to pay him $100 as a reward. A cannot enforce this promise, because: (1) it rests on a past consideration; (2) A was under a legal duty to return the automobile to its owner. Suppose there had been no legal obligation to return the found automobile, but only a moral obligation. The promise could not be enforced in that case, for the law will not concern itself with moral obligations or ethical considerations. It is not necessary that the promisor (the one who makes the promise) receive any benefit from the consideration given by the promisee. For instance, A promises to give B his $50 watch if B will paint C's barn. B does so, after obtaining the consent of C; he can force A to give him the watch, even though A may not have received any benefit from what B has done. Where the consideration itself is illegal, no legal contract results. Thus, A promises to pay B $100 if B will steal some papers from C. B gets the papers, but he cannot recover the $100, because what he has done is illegal. Promises to pay money lost in gambling cannot be enforced, since all gambling contracts are illegal. At common law a contract under seal need not be based on a consideration, it being held either that the seal imports a consideration or takes the place thereof. This rule is now altered by statute in many jurisdictions, which either makes a seal merely prima facie evidence of consideration, or abolishes the difference between sealed and unsealed instruments.