What is law like? What can we compare it with in order to illuminate its character and suggest answers to some of the perennial questions of jurisprudence?
Natural lawyers compare laws to moral propositions. A human law is an attempt by someone who has responsibility for a human community to replicate, publicize, and enforce a proposition of objective morality such as "Killing is wrong." Law is like moral reasoning, say the natural lawyers, and laws should be regarded as principles of right reason (principles that reason dicatates as answers to the moral questions that need to be addressed in human society). However, in recent times legal philosophers have looked for illumination in the domain of social fact rather than in the realm of value. Law is like power, they have suggested, or like certain facts about the existence and exercise of power. So, for example, John Austin, writing in the first half of the nineteenth century, said that laws were like commands. A command is the expression of a wish coupled with the threat of a sanction, and a law expresses the wish of a sovereign along with a threat (for the event of noncompliance) that the sovereign's ascendancy in a society makes credible. Justice Holmes offered a different comparison: a law, he said, is like a prediction of what courts will do in a certain event. The law prescribing fifty-five mph as the speed limit for the state of New York is a prediction that the courts will impose fines on those who are caught driving faster than that. So jurisprudence is like social science: it takes a series of predictions about what powerful people will do and it tests and organizes them.