Published online by Cambridge University Press: 01 April 2022
L. Jonathan Cohen has written a number of important books and articles in which he argues that mathematical probability provides a poor model of much of what paradigmatically passes for sound reasoning, whether this be in the sciences, in common discourse, or in the law. In his book, The Probable and the Provable, Cohen elaborates six paradoxes faced by advocates of mathematical probability (PM) when treating issues of evidence as they would arise in a court of law. He argues that his system of inductive probability (PI) satisfactorily handles the issues that proved paradoxical for mathematical probability, and consequently PI deserves to be thought of as an important standard of rational thinking. I argue that a careful look at each of the alleged paradoxes shows that there is no conflict between mathematical probability and the law, except when for reasons of policy we opt for values in addition to accuracy maximization. Recognizing the role of such policies provides no basis for questioning the adequacy of PM. The significance of this critical treatment of Cohen's work is that those interested in revising the laws of evidence to allow for more explicitly mathematical approaches ought to feel that such revisions will not violate the spirit of forensic rationality.
The author would like to thank Professor Walter Reiser for a helpful discussion of the law of evidence relating to “inference upon inference“ and for providing him with materials to study further this part of the law. The author would also like to thank Professor Henry E. Kyburg, Jr., the participants of the 1984 NEH Summer Seminar on Probability and the Philosophy of Science, Judith Jarvis Thomson, and a referee for Philosophy of Science for helpful comments on an earlier version of this paper. Finally, the author would like to acknowledge the The National Endowment for the Humanities, The Rockefeller Foundation, and The Center for Philosophy and Public Policy at the University of Maryland for providing opportunities to work on this paper.