In the main, the course of philosophic thought since the time of Leibniz has been such as to render almost self-evident his limitations, and to suggest needed corrections and amplifications. Indeed, it is much easier for those whose thoughts follow the turn that Kant has given modern thinking to appreciate the defects of Leibniz than to realize his greatness. I have endeavored, therefore, in the body of the work, to identify my thought with that of Leibniz as much as possible, to assume his standpoint and method, and, for the most part, to confine express criticism upon his limitations to the final chapter. In particular, I have attempted to bring out the relations of philosophy to the growing science of his times, to state the doctrine of pre-established harmony as he himself meant it, and to give something like consistency and coherency to his doctrine of material existence and of nature. This last task seemed especially to require doing. I have also endeavored to keep in mind, throughout, Leibniz's relations to Locke, and to show the "Nouveaux Essais" as typical of the distinction between characteristic British and German thought. JOHN DEWEY. _May_, 1888. CONTENTS. CHAPTER I. The Man. PAGE His Parents 1 His Early Education 2 His University Training at Leipsic 4 At Jena 8 At the University of Altdorf 10 His Removal to Frankfurt 10 His Mission to Paris 11 Discovery of the Calculus 12 Librarian at Hanover 13 His Activities 14 His Philosophic Writings 15 His Ecclesiastic and Academic Projects 17 His Later Years and Death 18 CHAPTER II. Sources of his Philosophy. Character of the Epoch into which Leibniz was born 20 The Thought of the Unity of the World 23 The two Agencies which formed Leibniz's Philosophy 24 The Cartesian Influences 26 Rationalistic Method 28 Mechanical Explanation of Nature 30 Application of Mathematics 32 Idea of Evolution 33 Interpretation of these Ideas 35