The prevailing system of rights and duties is designed to regulate the conflicting purposes of men. An established right is a promise that a certain kind of behavior will be backed by the organized force of the state or at least by the sentiment of the community; a duty is a promise that failure to respect the rights of others in a certain way will be punished. The punishment may be death, imprisonment, loss of property, the nullification of a right, the expression of disapproval. In short, the system of rights and duties is the whole system of promises which the courts and public sentiment will support. It is not a fixed system. It varies from place to place, and from time to time, and with the character of the tribunals and the community. But none the less it makes the conduct of men somewhat rational, and establishes a kind of union in diversity by limiting and defining the freedom with which conflicting purposes can be pursued. Sometimes the promises are embodied in coercive law: Thou shalt, on penalty of this, do that; thou shalt not do so and so. Sometimes the promise is based on a contract between two parties: there is no obligation to make the contract, but, once made, it must be executed or a certain penalty paid. Sometimes the promise is based on an ecclesiastical code: it must be followed or the wages of sin will be visited either in fact or in anticipation upon the sinner. Sometimes the promise is based on custom: it must be respected or the price of nonconformity, whatever it may happen to be, must be paid. Sometimes the promise is based on habit: it must be executed or the disturbance faced which men feel when they break with their habits. The question of whether any particular right or duty shall be enforced, the question of how it shall be enforced, whether by the police, by public criticism or private conscience, will not be answered by reasoning _a priori_. It will be answered by the dominant interests in society, each imposing to the limit of its powers the system of rights and duties which most nearly approximates the kind of social harmony it finds convenient and desirable. The system will be a reflection of the power that each interest is able to exert. The interests which find the rule good will defend it; the interests which find it bad will attack it. Their arguments will be weapons of defense and offense; even the most objective appeal to reason will turn out to be an appeal to desert one cause and enlist in another. 4 In the controversies between interests the question will be raised as to the merits of a particular rule; the argument will turn on whether the rule is good, on whether it should be enforced with this penalty or that. And out of those arguments, by persuasion or coercion, the specific rules of society are made, enforced and revised.