This book describes the Buddhism of India on the basis of the comparison f all the available original sources in various languages. It falls into three approximately equal parts. The first is a reconstruction of the original Buddhism presupposed by the traditions of the different schools known to us. it uses primarily the established methods of textual criticism, drawing out of the oldest extant texts of the different schools their common kernel. The kernel of doctrine is presumbly common Buddhism of the period before the great schisms of the fourth and third centuries B.C. It may be substantially the Buddhism of the Buddha himself, though this cannot be proved: at any rate it is a Buddhism presupposed by the schools as existing about a hundred years after the Parinirvana of the Buddha, and there is no evidence to suggest that it was formulated by anyone other than the Buddha and his immediate followers.The second part traces the development of the 'Eighteen schools' of early Buddhism, showing how they elaborated their doctrines out of the common kernel. Here we can see to what extent the sthaviravada, or 'Theravada" of the Pali tradition, among others, added to or modified the original doctrine. The third part describes the Mahayana movement and the Mantrayana, the way of the bopdhisattva and the way of ritual. The relationship of the Mahayana to the early schools is traced in detail, with its probable affiliation to one of them, the Purva Saila, as suggested by the consensus of the evidence.