From later antiquity down to the close of the eighteenth century, most philosophers and men of science and, indeed, most educated men, accepted without question a traditional view of the plan and structure of the world. In this volume, which embodies the William James lectures for 1933, Arthur O. Lovejoy points out the three principles—plenitude, continuity, and graduation—which were combined in this conception; analyzes their origins in the philosophies of Plato, Aristotle, and the Neoplatonists; traces the most important of their diverse samifications in subsequent religious thought, in metaphysics, in ethics and aesthetics, and in astronomical and biological theories; and copiously illustrates the influence of the conception as a whole, and of the ideas out of which it was compounded, upon the imagination and feelings as expressed in literature.