science in this branch of celestial statics and dynamics. THOMAS HOBBES. It has been shown that one momentous effect of the Copernican astronomy, as interpreted by Giordano Bruno, was to reverse the relative importance ascribed in Aristotle's philosophy to the two great categories of Power and Act, giving to Power a value and dignity of which it had been stripped by the judgment of Plato and Aristotle. Even Epicurus, when he rehabilitated infinite space, had been careful as a moralist to urge the expediency of placing a close limitation on human desires, denouncing the excesses of avarice and ambition more mildly but not less decisively than the contemporary Stoic school. Thus Lucretius describes his master as travelling beyond the flaming walls of the world only that he may bring us back a knowledge of the fixed barrier set by the very laws of existence to our aspirations and hopes. The classic revival of the Renaissance did not bring back the Greek spirit of moderation. On the contrary, the new world, the new astronomy, the new monarchy, {23} and the new religion combined to create such a sense of Power, in contradistinction to Act, as the world had never before known. For us this new feeling has received its most triumphant artistic expression from Shakespeare and Milton, for France from Rabelais, for Italy from Ariosto and Michelangelo. In philosophy Bacon strikes the same note when he values knowledge as a source of power--knowledge which for Greek philosophy meant rather a lesson in self-restraint. And this idea receives a further development from Bacon's chief successor in English philosophy, Thomas Hobbes (1588-1679), in whose system love of power figures as the very essence of human nature, the self-conscious manifestation of that Motion which is the real substance of the physical world.