I ?nd it impossible to write a preface to this work, without discovering a little of the enthusiasm which I have contracted from an attention to it. Joseph Priestley. The History and Present State of Electricity. It is generally considered bad form in writing, unless on matters autob- graphic, tomakeunbridleduseoftheperpendicularpronoun. Thereaderof the present book, however, may well wonder why one would want to study 1 the life and works of Thomas Bayes, ‚this strangely neglected topic‘ , and it is only by a reluctant use of the ?rst person singular on the part of the author that this legitimate question can be answered. It was in the late 1960s that my interest in various aspects of subjective probability was awakened by some of the papers of I. J. (‚Jack‘) Good, and this was followed by the reading of works such as Harold Je?reys’s Theory of Probability. In many of these the (apparently simple) result known as Bayes’s Theorem played a pivotal r ole, and it struck me that it might be interesting to ?nd out a bit more about Thomas Bayes himself. In trying to satisfy this curiosity in spasmodic periods over many years I discovered that little information seemed to be available. Writings by John D.