The Modern PHILOSOPHY SERIES Tlarged de in Student's Lies of volumes containing writings of the great philosophers. These volumes are edited by the most competent authorities at home and abroad. The selections are comprehensive and suited to the special needs of students and the general reading public. Each volume contains an introduction giving a brief outline of the system of the author and indicating his place in the history of thought. HE Modern Student's Library has been en The Philosophy Series is under the general editorship of Ralph Barton Perry, Professor of Philosophy, Harvard University. [For a complete list of THE MODERN STUDENT'S CHARLES SCRIBNER'S SONS INTRODUCTION PLATO has exerted a greater influence over human thought than any other individual with the possible exception of Aristotle; this is due both to the intrinsic vitality of his ideas and to the fact that he appears at a comparatively early stage in Western culture. His ideas affect the intellectual climate of our day in two important ways: first, by entering into our Christian theology and contributing especially to its doctrine of the opposition between the spirit and the flesh; secondly, by entering into our scientific mentality. The fundamental assumption of modern science is the importance of the mathematical method in the understanding of things, and this was Plato's cherished doctrine. Moreover, from amongst the works of the ancient Greek writers, those of Plato alone have survived in their totality. Undoubtedly, the leading factor in the remarkable preservation of the Platonic writings was the existence of the Platonic Academy, founded in 387 B. C. and enjoying a life of about eight centuries up to 529 A. D., when its funds were embezzled by Justinian. A philosopher in our day is considered a specialist in a field of knowledge distinct from that of science. Plato was a philosopher in a totally different sense. For him, philosophy was insight into the whole of truth, the study of reality in all its aspects; he was unaware of any barriers between this or that field of inquiry such as we erect today. Common sense ran into physics, physics into mathematics, mathematics into metaphysics; metaphysics, in its turn, led into ethics, politics, and religion. In reading the dialogues of Plato, we find abstruse discussions of ultimate principles joined to |