Although the elder civilizations of Assyria and Egypt boasted a cultivation of astronomy long anterior to the heroic age of Greece, their cosmographical ideas appear to have been rude and undeveloped, so that whatever the Greeks borrowed thence was of small importance compared with what they themselves ascertained. While it may be doubted if decisive testimony can be extorted from the earliest Grecian literature, represented chiefly by the Homeric and Hesiodic poems, it is probable that the people among whom that literature grew up had not gone, in their conception of the universe, beyond simple acceptance of the direct evidence of their senses. The earth they looked upon as a plane, stretching away from the Ægean Sea, the focus of their knowledge, and ever less distinctly known, until it ended in an horizon of pure ignorance, girdled by the deep-flowing current of the river Oceanus. Beyond Oceanus even fancy began to fail: there was the realm of dust and darkness, the home of the powerless spirits of the dead; there, too, the hemisphere of heaven joined its brother hemisphere of Tartarus.[259] This conception of the earth was not confined to Homeric times, but remained the common belief throughout the course of Grecian history, underlying and outlasting many of the speculations of the philosophers. That growing intellectual activity which was signalized by a notable development of trade and colonization in the eighth century, in the seventh awoke to consciousness in a series of attempts to formulate the conditions of existence. The philosophy of nature thus originated, wherein the testimony of nature in her own behalf was little sought or understood, began with the assumption of a flat earth, variously shaped, and as variously supported. To whom belongs the honor of first propounding the theory of the spherical form of the earth cannot be known. It was taught by the Italian Pythagoreans of the sixth century, and was probably one of the doctrines of Pythagoras himself, as it was, a little later, of Parmenides, the founder of the Eleatics.[260] In neither case can there be a claim for scientific discovery. The earth was a sphere because the sphere was the most perfect form; it was at the centre of the universe because that was the place of honor; it was motionless because motion was less dignified than rest.