The result of all these factors was the birth of Greek rationalism and real genesis of science and philosophy in sixth century Ionia. The Ionian philosopher-scientists asked
“why” concerning the world and its phenomena and sought to make consistent and logical generalizations about nature. And unlike any before them they did not do so from religious or purely practical motives, but from simple curiosity, from the plain desire to understand and order the world about them. This is the crux of rationalism. The Near Eastern societies had developed a considerable body of scientific knowledge, but they had done so in the service of religion or practical needs and in a context of mythopoeic thought. The impressive engineering skills of the Egyptians, for example, followed upon the desire to build more elaborate temples and tombs for their god-kings, and the sophisticated astronomical data of the Babylonians was collected in order better to read the will of the gods revealed in the movements of the heavenly bodies. And whatever the motives, the mythopoeic outlook of the pre-classical societies, a world view that rejected logic, consistency, generalization and natural causation, prevented them from turning their accumulation of data into true science and philosophy. Now in Greece for the first time in any significant numbers men were studying the world around them simply to understand it and were realizing that through such understanding the human condition could be improved.
The skepticism of the Ionian thinkers was especially strong regarding the inherited religious traditions, understandably, since reason naturally tends to devalue ideas based only on faith and custom. The Ionian scientists were breaking the mythopoeic bonds and spurning the divine in their explanations of things; the traditional mythos was being challenged by the newly discovered logos. It was a rare Greek thinker who did away with divinity altogether and almost all accepted the notion of some divine first principle, but in their examination of the cosmos they focused their attention on impersonal forces and natural causation. “For many and ridiculous,” says Hecateaus of Miletus (fl. c. 500) at the end of the sixth century about the inherited traditions, “so they seem to me, are the tales of the Greeks.” Far more astounding is the declaration of his contemporary Xenophanes: “And if oxen and horses and lions had hands, and could draw with their hands and could do what man can do, horses would draw the gods in the shape of horses, and oxen in the shape of oxen, each giving the gods bodies similar to their own.” In other words, the gods are mere inflations of the mortal image, which is an incredibly penetrating perception about the nature of religion, one that has not occurred to most people even today.
Thales of Miletus (fl. c. 600), earliest known of the Ionian thinkers, saw the material world as being formed of or evolved from a single substance – water. This is of course not quite right, but the systematic generalization and rational speculation involved in reaching such a conclusion was a great achievement. Thales expressed (or at least implied) for the first time the essential scientific-philosophical concept of form, that is, the idea that substance and form are separate qualities. This might seem a completely obvious conclusion, but it certainly was not to people before Thales. Mythic thought views every object as completely unique and makes no distinction between form and substance.
Anaximander of Miletus (fl. 1st half 6th cent.), a younger contemporary of Thales, elaborated on his colleague’s ideas, and in his view of the development of the material world he came up with a fantastic notion. He suggested that the first generations of men were nurtured inside of fish-like creatures, which had themselves arisen spontaneously in the primeval seas. His belief that land animals, including humans, came originally from the sea is hardly a statement of Darwinian evolution, but it is nevertheless a brilliant breakthrough. Every previous conception of the origins of man had made him a special creation of the gods, either spit out or ejaculated or fashioned out of dirt or some other handy material. And here is Anaximander laying a firm foundation for an understanding of the evolution of life on the planet by dethroning man and placing him squarely in the animal kingdom.
This kind of thought is a triumph of human reason, proceeding to inquire into first principles from a basis of general physical observation. It would take the Greeks (that is, the educated elites) a while to emancipate themselves completely from the concrete imagery of mythopoeic thought, but the basic break with myth had taken place, virtually overnight. The headlong plunge into rationalism was in fact overbold: so drunk were these new rationalists on the novel notions of logic and consistency, both foreign to mythic thought, that they followed them wherever they led, even if that meant contradicting the observed world. This resulted in many mistaken ideas about the nature of things, but it nevertheless demonstrated an intellectual courage impressive in any age, as the Ionians accepted without hesitation logical conclusions that were at odds with what they saw about them.
The mythopoeic mode of thought of the pre-Greek cultures certainly worked; the longevity and achievements of these societies attest to that. But it was simply an incorrect view of the universe and placed a very low ceiling on intellectual progress. In the belief systems of these societies, including the Hebrews, man was fashioned essentially to serve the gods. True, the Egyptians provided him with some measure of dignity by understanding him to be an integral part of creation, akin to the animals and the gods, but it was a static conception that left the human potential untapped. The Greeks now dared suggest that man was not a special creation of the gods, but at the same time they boldly asserted that he did indeed occupy a special place, not because of any particular relationship with god, but because of his mind. The birth of humanism and rationalism was the discovery of the mind, the realization that unlike the other inhabitants of creation humans could examine and refashion their world and even themselves. For a moment at least, the obsession with the established order, prevalent in Greece as it had been in the Near Eastern societies, was shattered, and invention and change were in the air. Unfortunately, that moment would pass, and by the second half of the fifth century Greeks would once again fear innovation, especially in the economic and social spheres, as a challenge to the status quo and thus a path to social upheaval and ruin. But while it lasted the moment was electrifying, and in any case the humanism and rationalism would remain, woven into the fabric of urban Greek society and the cause of a spectacular cultural outburst. After two and a half millennia of human civilization the Greeks had finally discovered man.