In the four "Transmutations Notebooks," which Darwin filled for two years while living in London after returning to England from the Beagle voyage, are a host of thoughts, observations, quotations from books he was reading and from conversations with friends, such that it is difficult to know exactly which of the ideas expressed in the notebooks belong to Darwin as part of "my theory," and which are simply passing thoughts to be considered and then rejected, but a statistical study of the frequency with which Darwin uses certain words indicates that during the course of the two years there were three theories of transmutation which he considered to be "mine" and that the host of other ideas which he expressed contemporaneously were either subsidiary to these or of only passing interest (with one major exception). 1 The question is, were these three theories complementary or were they mutually exclusive? If they were complementary, then the implication is clearly in favor of the importance of the empirical data in shaping Darwin's thought, but if they were mutually exclusive, the implication is that Darwin approached the data with a prior world view which he attempted to superimpose on the data by means of various hypothetical models and mechanisms.
This paper begins with an account of Darwin's dispute with Robert Fitzroy, captain of the Beagle, over the nature and origin of the Gal~pagos finches. It describes how the dispute is settled by John Gould, ornithologist of the Zoological Society of London, when he takes Fitzroy's side by declaring the finches to be real species. A brief description of Gould's career is given in order to clarify Darwin's relationship to him. Next is shown how Darwin reconciles his interpretation of the origin of the Gal~ipagos finches with Gould's classification of them by supposing that all species are mutable. This starts him off on the long quest for the secret of the origin of species. After watching 1. G.J. GrinneU, "The Darwin Case: A Computer Analysis is Scientific Creativity," unpub, diss