The problem which lay before the earliest philosophers of Greece was how to emerge from mythological conceptions concerning the origin and nature of the world into a region of more exact and abstract thought. They had their list of demiurgic agencies, Titans and deities, some of them dramatically personified in the poems of Homer and the legends of Olympus, others but vaguely indicated by the names of Earth and Ocean, Heaven and Time. The polytheistic and mythologizing instincts of the race at large tended to individualize these primal powers with more and more distinctness, collecting legends around the more popular among them, and attributing moral sympathies and passions to those who were supposed to have relations with humanity. But there remained a background of dimly descried and cloudy forces upon which the mythopoeic imagination had taken little hold; and these supplied a starting-point for scientific speculation. It was in this field that the logical faculty of the Greek mind, no less powerful and active than its poetic fancy, came first into play. Thus we find Thales brooding in thought upon the mythus of Oceanus, and arriving at the conception of water as the elementary principle of the universe; while Gaia, or Earth, in like manner is said to have stimulated Pherecydes. Anaximenes is reported to have chosen air as the groundwork of his cosmogony, and Heraclitus developed the material world from fire. It must not be supposed that any of these early speculators invented a complete hypothesis for deducing phenomena from earth, air, fire, or water as apprehended by the senses. Their elements, or #archai#, are rather to be regarded in the light of symbols--metaphors adopted from experience for shadowing forth an extremely subtle and pervasive substance, a material of supersensible fluidity and elasticity, capable of infinite modification by rarefaction and condensation. At the same time they were seeking after intellectual abstractions; but the problems of philosophy as yet presented themselves in crude and concrete form to their intellects.