There are *cases in which a promise should not be kept.* The promise to perform an immoral act is void from the beginning. It is wrong to make it, and a double wrong to keep it. The promise to perform an act, not intrinsically immoral, but unlawful, should be regarded in the same light. If both parties were aware, when the promise was made, of the unlawfulness of the act, then neither party has the right to deem himself injured by the other. If, however, the promiser was aware of the unlawfulness of his promise, while the promisee supposed it lawful, the promiser, though not bound by his promise, is under obligation to remunerate the promisee for his disappointment or loss. If the act promised becomes unlawful between the making and the execution of the promise, the promise is made void, and the promisee has no ground of complaint against the promiser. Thus, if a man promised to send to a correspondent goods of a certain description at a certain time, and before that time the exportation of such goods were prohibited by law, he would be free both from his promise and from responsibility for its non-fulfilment. A promise neither immoral nor unlawful, but made under a mistake common to both parties, and such as—had it been known—would have prevented the promise, is void. An extorted promise to perform an immoral or unlawful act cannot be binding. One has, indeed, no moral right to make such a promise, though if the case be one of extreme urgency and peril, extenuating circumstances may reduce the wrong to an infinitesimal deviation from the right; but, when the duress is over, no considerations can justify the performance of what it was wrong to promise. But a promise, not in itself immoral or unlawful, is binding, though made under duress. Thus, if a man attacked by bandits has had his life spared on condition of a pecuniary ransom, he is bound to pay the ransom; for at the moment of peril he thought his life worth all he promised to give for it, and it is neither immoral nor unlawful to give money, even to a robber. In a case like this, regard for the safety of others should, also, have weight; for in a country liable to such perils, the breach of a promise by one man might cost the community the lives of many. *Contracts* are mutual promises, in which each party puts himself under specific obligations to the other. They are to be interpreted on the same principles, and to be regarded as void or voidable on the same grounds, with promises.