Although few would dispute that law and philosophy developed from the same tradition or even that law uses philosophical concepts, a premise of much legal scholarship is that law has developed its own methodology and is wholly separate from philosophy. This attitude may reflect, in part, a feeling that philosophy is more esoteric or difficult than law, and that lawyers are ill-equipped to venture into philosophical thickets. It is true, of course, that philosophers often think about issues far removed from pragmatic reality while lawyers have to deal with real cases and real people.

But law and philosophy cannot be so easily divorced. Indeed, judicial opinions can be seen as forming a data set that permits rough tests of philosophical concepts. While an individual case may reach an aberrant result, a relatively stable judicial concept will likely emerge over time. Perhaps courts define philosophically-related concepts differently than philosophers, but I think that unlikely. Philosophers do not invent philosophical accounts, and judges do not invent interpretations of legal concepts. Both groups draw from the surrounding culture.

One way to gain insight into cultural attitudes toward a particular question is to look for similarities in legal and philosophical treatments of that question. I wish to examine one potential parallel between law and philosophy by comparing the prevailing judicial account of coerced self-incrimination with the prevailing philosophical treatment of coercion. I will focus on the question of when, in particular cases, the police (P) coerce a suspect (S) into answering questions (A). The principal source of legal protection against this kind of coercion is the Fifth Amendment self-incrimination clause. The clause provides that "No person ... shall be compelled in any criminal case to be a witness against himself. As the clause prohibits compulsion rather than coercion, I begin with the assumption that compulsion and coercion are co-extensive concepts, an assumption I will later question. Moreover, I am interested only in coercion that causes (or will cause) an incriminating response. The extent to which government can penalize a refusal to testify - when the coercion is resisted - is a wholly separate question.