Traditionally regarded as the first Western philosopher and mathematician, Thales of Miletus (a Greek colony on the west coast of present day Turkey) lived c. 585 BCE. He accurately predicted the solar eclipse of May 28, 585 BCE and was known as a skilled astronomer, geometer, statesman and sage. Thales, it is said, was the first to ask the question, “What is the basic 'stuff' of the universe” and, according to Aristotle, claimed the First Cause was water because, among other attributes, water could change shape and move while still remaining unchanging in substance. There are no known writings by Thales and all that is known of his life and work is through what we have written about him by others.
Aristotle tells the story of how Thales proved to his contemporaries the practical use of philosophy:
When they reproached him because of his poverty, as though philosophy were no use, it is said that, having observed through his study of the heavenly bodies that there would be a large olive crop, he raised a little capital while it was still winter, and paid deposits on all the olive presses in Miletus and Chios, hiring them cheaply because no one bid against him. When the appropriate time came there was a sudden rush of requests for the presses; he then hired them out on his own terms and so made a large profit, thus demonstrating that it is easy for philosophers to be rich, if they wish, but that it is not in this that they are interested.
There seems to be no subject which was not of interest to Thales but, according to Aristotle (in his Metaphysics) he was chiefly concerned with the First Cause - that from which all else came - and declared it to be water. Some scholars have claimed that Thales derived this concept from the ancient Greek paradigm of the universe in which, in the beginning, all was undifferentiated chaos in the form of water, while others have claimed that Thales learned the concept while studying in Babylon. According to Aristotle and other writers of antiquity, Thales was regarded as an original thinker and his `water theory' does not bear a close relationship with the Greek mythological assertion nor with any Babylonian texts which have come down to us. While Thales does assert, as the Greek myth does, that the earth rests on water, Thales' theory dismisses any supernatural causes for this state of being. For Thales, there were practical, provable, logical reasons for why things happened and the gods had nothing to do with observable phenomena.
With this in mind, it is interesting to note that another of Thales' famous claims was that "All things are full of gods". In his De Anima, Aristotle writes, "Thales, too, to judge from what is recorded of his views, seems to suppose that the soul is in a sense the cause of movement, since he says that a stone [magnet, or lodestone] has a soul because it causes movement to iron’ (405 a20-22). What, exactly, Thales meant by this statement is unclear but it has been suggested, and is probable, that by `gods' he simply meant energy and that Plato later re-interpreted Thales' statement according to his own idealism and popularized it.
Thales founded the Milesian School which, today, would equate with a private college at which young men could pursue a course of study in debate, investigation, and exploration of the world around them. While there is no evidence that Thales was an atheist or that he taught atheism, there is ample evidence that the traditional understanding of the gods had no place in his teachings. His most famous pupil, Anaximander, carried on this same point of view as did Anaximenes, also of the Milesian School, after him.
Among his many achievements, Thales `discovered' Ursa Minor, studied electricity, developed geometry, contributed to the practical application of mathematics later developed by Euclid, studied in Egypt and, perhaps, Babylon, developed a crude telescope, `discovered' the seasons and set the solstice, created what would later be known as `natural philosophy', and was recognized, along with illustrious men like Solon, as one of The Seven Sages of Ancient Greece (first mentioned in Plato's dialogue of the Protagoras). According to Diogenes Laertius, "This wise Thales died while present as a spectator at a gymnastic contest, being worn out with heat and thirst and weakness, for he was very old, and the following inscription was placed on his tomb: You see this tomb is small—but recollect, The fame of Thales reaches to the skies." While later philosophers disagreed with Thales’ claim that water was the First Cause and basic substance of the universe, his work inspired those who would come to be known as the Pre-Socratic Philosophers to pursue their own paths and develop their own philosophical systems which would finally culminate in the vision of Socrates and have resonance far beyond the ancient world.