If we need a figure to indicate the way in which the influence of Plato has passed through Europe, we must liken it, not to a river continually at the flood, but to an expanding atmosphere enveloping and pervading whatever it meets, an atmosphere with a perfume that has made some sick and others open their nostrils to take in the seed and substance of a new life. A river makes a linear path which, except perhaps for a few sinuosities and an occasional overflow, can be traced with relative ease; but an atmosphere, enlarging itself in all dimensions, with attenuation here and condensation there and precise limits nowhere, offers neither clue nor pattern for the inquisitive historian who would, seek to plot its course. We may be prepared to find it anywhere. So it is with the metaphysics of Plato. No sphere of learning or of art has kept beyond its reach. Anyone who, by comprehending its particular incidence and its total range, would write the most remarkable single chapter in the history, of thought, would have to search the minds not merely of philosophers but also of saints, scientists, poets, painters, sculptors, statesmen, and educationists of all ages. He would even have to search for the breath of it among the innumerable works of fiction that tumble mechanically from our modern undiscriminating presses. The following, for example, is pure Platonism: “We come from a world where we have known incredible standards of excellence, and we dimly remember beauties which we have not seized again; and we go back to that world. Uncle Pio and Camila Perichole were tormenting themselves in an effort to establish in Peru the standards of the theatre in some heaven whither Calderon had preceded them.” To understand, alike in its emotional beauty and in its scientific severity, the metaphysic that underlies such charming phrases is perhaps an obligation, almost a necessity, and certainly a privilege.