The Greeks invented, among other things, science and philosophy. The first scientists and philosophers lived during the sixth century B.C. on the Greek coast of Asia Minor and in the Greek cities of southern Italy. Later, during the fifth and fourth centuries, the important centre of thought was Athens. But by this time science and philosophy were studied everywhere in the Greek world. These studies shaped the civilization of Rome and, in many respects, the theology and ethics of the Christian churches. They were revived in something more like their original form at the time of the Renaissance. They have transformed the whole of mankind.
It would be an exaggeration to say that before the time of Thales of Miletus men were incapable of rational thought, but there would be some truth in the statement, since before his time it does not appear that anyone asked those precise questions out of which science and philosophy were to develop. The questions were "What is everything made of?", "How do things come into being, change and pass away?", "What permanent substance or sub-stances exist behind appearances? " And these questions, of course, led on to others connected with the existence of the gods, the laws of nature and the duties or purpose of man upon the earth.
The originality was both in the asking of the questions themselves and in the assumption made with regard to how they could be answered. It was assumed, for the first time in history, that the investigator was dealing with a universe that was a "cosmos" — that is to say an orderly system governed by laws which could be discovered by logical thought and by observation.
Of course this assumption, in a limited way, had been made previously. No form of civilization at all would be possible if it were not generally believed, for example, that spring would invariably follow winter. And the civilizations of Mesopotamia and of Egypt, with both of which the Greeks were acquainted, had already made remarkable discoveries on the basis of the observed regular movements in nature. The Babylonians were able to predict eclipses, though, being ignorant of their true causes, they did not know whether a particular eclipse would in fact be visible from Babylonia. They watched for the eclipses at the right times and regarded it as a good omen if the eclipse did not appear. There was, as it were, on the one side a certain number of observed recurrent phenomena, and on the other side a great realm of experience which was regarded as unpredictable and irrational, though in some ways open to influence by means of magic or religious observances.
It was a state of affairs at which the Roman poet Lucretius, a contemporary of Julius Caesar, writing some five hundred years after the original revolution of thought, looked back. He wrote:
There was a time when the life of men was something evidently quite foul. Mankind was grovelling on the ground, pressed down beneath the heavy weight of superstitious awe. This superstitious awe (Religion, one may call it) proudly showed her head in every quarter of the sky and with an aspect of terror stood over and looked down on mortal man. It was a man from Greece who first dared to raise defiantly his mortal eyes and then to take his stand against her. He could not be suppressed by stories about the gods or by thunderbolts or by a sky full of the menace of thunder. On the contrary, these things were an incentive to the cutting genius of his mind. They made him all the more ready to be the first man on earth to want to break through the bolts fitted across the doors of reality. And so this vital vigour of his spirit won a total victory. His campaign carried him far beyond the flaming barriers of the sky. By sheer force of intellect he was able to wander over the whole of infinity. From this journey he brings back to us the fruits of victory-the knowledge of what can and what cannot come into existence, what are the fixed limitations to the powers of each individual thing and the sharply drawn line of definition. So now it is the turn of Religion to be cast down and trampled underfoot. As for us, the victory has raised us up to the skies.
Lucretius, of course, was writing of Epicurus, and Epicurus was not "the first man who dared to raise his eyes." Then, too, Lucretius writes with the rather exaggerated fervour of a convert. It is by no means true that Greek philosophy is necessarily anti-religious. Yet still the general picture given by Lucretius is not far from the truth. Something really unique and revolutionary had happened when Thales, for whatever reasons, came to the conclusion that there was a fundamental substance and that this substance was water. As for superstition, it had certainly not died out at the time of Lucretius and it has not died out yet. Nevertheless it is impossible to deny that the "victory" was a real one.
As for the precise doctrines of many of these early philosophers, there is often considerable difficulty in discovering them and in understanding them. Partly the difficulties proceed from lack of material. Partly the difficulty is in the nature of things, since this new invention of rational thought only gradually invented its own vocabulary. The early thinkers did not call themselves "philosophers" and took some time before they became logicians. Such notions as "substance," "matter," "mind," "element," "atom," "force" — even "thing" and "event" — were not ready to hand; the words for them did not exist. Words had to follow thought, so that it is impossible that the original thought should have been clearly and neatly expressed.
Nor, of course, was there at first any close distinction between philosophy and science. There was not even (in spite of what Lucretius says) a distinction between these and religion. The investigation was into Phusis, the nature of things — what things are, how they come into being. And here Lucretius writes well about "the fruits of victory."