Jurisprudence

Jurisprudence has always been a wild card in the legal deck. While the dictionary allows it may be the ''science or philosophy of law,'' no two commentators agree on its meaning, still less its relationship with what lawyers think of as real law. Even so, a distinctive form of jurisprudence has gradually emerged in this country. Its most conspicuous attribute has been an obsessive concern with judges and the judiciary.

In the late 19th century, Lord Acton said there had been six American political theorists of the first rank and that all of them had served in public office. If the principle he implied is right, then we might reasonably expect judges to be our leading jurisprudential thinkers. After all, they have the obligation to declare the unwritten common law, to interpret the written law and to apply both in specific cases. Their decisions are also subject to the scrutiny of parties to every lawsuit (one of whom is invariably aggrieved), of members of the legal profession, and, in the occasional sensational case, of the general public. So they have reasons to worry about the nature of legal authority and about justifications for their decisions. And indeed a remarkably high proportion of our most influential writers on jurisprudence - from Chancellor James Kent and Justice Joseph Story in the early 19th century to Justices Oliver Wendell Holmes and Benjamin Cardozo and Judges Learned Hand and Jerome Frank - have sat on the bench.

American jurisprudence thus came to focus on the judiciary. And this concern has contributed to the development of a legal system that differs from that of other nations precisely in the relative importance we place on courts. Judge Posner's book reflects the tradition of American judges driven to jurisprudence in search of justifications for legally ''right'' answers. It also reflects the modern academic lawyer's tendency to look beyond conventional legal authority to extralegal sources, including philosophy, the social sciences and the humanities, for a deeper understanding of the legal enterprise.