This is a history of the use of Bayes's theorem over 150 years, from its discovery by Thomas Bayes to the rise of the statistical competitors in the first third of the twentieth century. In the new edition, the author's concern is the foundations of statistics, in particular, the examination of the development of one of the fundamentai aspects of Bayesian statistics. The reader will find new sections on contributors to the theory omitted from the first edition, which will shed light on the use of inverse probability by nineteenth century authors. In addition, there is amplified discussion of relevant work from the first edition. This text will be a valuable reference source in the wider field of the history of statistics and probability.