The reasons that prompt people to try to identify laws or legal systems in advance of encounter are varied. One is that laws, though less concrete than chairs, are equally capable of posing obstacles to conduct: they can be stumbled over. If the desire to avoid such contact were the sole reason for trying to decide "what law is,'' Holmes' aphorism would work fairly well: by predicting judicial decisions and calculating the likelihood of avoiding accompanying sanctions, one could play a good game of "bad man's" bluff around legal obstacles to chosen courses of action.

The claim that law is identified by more than this predictive aspect arises when one takes into account the perspective of individuals other than Holmesian "bad men"-the judge, for example, who looks to the law as a guide for, rather than a prediction of, his decision; or the individual who believes that valid norms yield obligations whether or not they are accompanied by sanctions.