This paper construes various positions in the philosophy of science and the philosophy of law as responses to the problem of underdetermination in science and in law. We begin by drawing a close analogy between the successive approaches to this problem in the two fields. In particular, we stress the analogy between conventionalism as a philosophy of science and legal realism as a philosophy of law, and between Putnam's and Dworkin's critiques of these positions. We then challenge the Putnam-Dworkin strategy, (...) arguing that their attempts to combat underdetermination are unsuccessful. We are thus led to scepticism regarding the outlook underlying the celebrated maxim, “ruled by law, not by men”. (shrink)