The main purpose of this book is to provide a collection and study of the extant evidence concerning the life and thought of Speusippus, Plato's nephew and his successor as head of the Academy. It must be emphasized that the collection of texts printed here is meant to be used in conjunction with the commentary. Also, those who intend to use the collection of texts even for purposes incidental to Speusippus should first read the Introduction to this work. I should like to thank the following individuals and institutions for their help and interest in my work: Professor Harold Cherniss discussed with me many problems related to Speusippus, Aristotle, and the early Academy. Professor Eric Turner gave generously of his time to talk with me about Crönert's theory concerning the Academicorum Philosophorum Index Herculanensis and was kind enough to write at length on it (cf. Appendix III). Professor Albert Henrichs provided me with a new text of F 57, sent me copies of his publications on Philodemus' De Pietate and corresponded with me on this subject. Professors Bernard Goldstein and David Pingree helped me with Arabic texts. Fellowships from the American Council of Learned Societies in 1971-72 and from the John Simon Guggenheim Memorial Foundation in 1975, membership at the Institute for Advanced Study, Princeton, NJ, in 1978-79, and two sabbatical leaves (1971-72 and 1978-79) from Columbia University made it possible to begin and finish this work. The Guggenheim Foundation and the Stanwood Cockey Lodge Foundation at Columbia University provided generous grants to defray the cost of publication.