Substance, beginning with Thales | Anaximander, many Substances and Harmonious Conflict | Pythagoras, the First Theologian | Xenophanes of Colophon | Heraclitus, Change and more anti-Homer | Anaxagoras and Science | Atoms, Science, Medicine and Journalism
The poet Tyrtaeus of Sparta, who lived around 650 BCE, proclaimed that the ultimate concern of man was the common good of his community – his polis. A century later a Greek named Thales (624–546) took philosopher further. He did what others did without thinking about it: he categorized. But he did so considering things that were at least largely ignored. Thales was born into a family of wealth. He had the leisure and energy to pursue learning and travel. He had the advantage of living in a time of literacy and trade, and he benefitted from cultural diffusion. He traveled from his city of Militus, in Asia Minor by the Aegean Sea, to Egypt, and he saw the use of simple and practical geometry in land surveying that the Egyptians had created. He was interested in the nature of things and he worked this geometry into a set of new mathematical principles. He became an engineer, and it is said that for King Croesus of Lydia he made the river Halyes passable by diverting its waters. Thales was also interested in heavenly bodies. In his travels he might have come into contact with the astronomical data that Babylonians had accumulated across the centuries, but he also made his own observations of the stars, and he predicted a solar eclipse.
As an engineer who manipulated things he thought the material world should be understandable, and it led him to speculate about reality's basic nature. What we know about Thales comes from the writings of Plato and Aristotle more than a century later. Aristotle wrote that Thales assumed that matter contained the first principles of reality. Thales is said to have found water as primary. He believed with his contemporaries that the world was flat and rested on a great body of water. He saw that water was necessary to live and that it was everywhere. He theorized that the world is in essence water and that it had originally been in the form of water – as if without moisture everything would become dust and nothingness. Or, as Aristotle speculated about Thales' view: "the nourishment of all beings is moist."
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