The doctrine of Pythagoras also deserves mention, for it has played a great rôle in history. He is said to have held that the whole world is, and that the life of man ought to be, harmoniously ordered in accordance with mathematical principles; nay more, that such principles are living things and that numbers are the essence of the universe. The logical conclusion is that by skilful use of mere numbers man can move heaven and earth. As the poet, eulogizing Michael Scot, put it; the “mathematici” by their art affect numbers, by numbers affect the procession of the stars, and by the stars move the universe. The employment of characters constructed of numbers or of geometrical figures, the use of numerical formulæ as remedies or of compounds of three portions of three kinds of drugs applied during three successive days, is raised from the plane of superstition to the level of science. It is not unreasonable to suppose that the heavenly bodies with their apparently unchanging regularity of movement are the governors of our existence. Plato, who adopted the Pythagorean doctrines at least to a considerable extent, declared that the loftiest function of the sense of sight was to survey the heavens, an occupation by which we gain philosophy.[118] Like the Pythagoreans also, he associated the four elements with regular solids. The cube represented earth; the octohedron was water; the tetrahedron, fire; and the icosahedron, air.[119] The remaining regular solid, the dodecahedron, was held to represent the universe as a whole. Towards magic, as he understood it, Plato’s attitude seems to have been sceptical, though perhaps not confidently so. He maintained that persons acquainted with medicine and prophets or diviners were the only ones who could know the nature of poisons which worked naturally, and of such things as incantations, magic knots and waxen images; and that since other men had no certain knowledge of such things, they ought not to fear but to despise them. He admitted, however, that there was no use in trying to convince most men of this and that legislation against sorcery was necessary.[120] He himself occasionally mentioned charms or soothsaying in a matter-of-fact way.