It sounds so easy for us now with what he discovered, but 2600 years ago, when other Greeks still had problems with addition and multiplication in their own way, he discovered or invented many things.
He was extraordinarily brilliant, a mathematician; among the first to contribute to Western geometry. He gave the Egyptian guide in awe the exact height of the pyramid he saw as 160 paces. He could make money and was wealthy. The very learned and exceptional Aristotle considered him as the first philosopher (probably in all 3, 4 fields of philosophy: metaphysics, logic, political philosophy, and ontology). As a primitive “scientist” he postulated that many things (or all) were made of water.
He is Thales of Miletus.
The Greek Mind was astonishingly fruitful for 5, 6 centuries right before Christ. Western philosophy, from the beginning, can be said as the gift of the Greek genius.
Typically historians of philosophy divide ancient Greek thinkers into the Pre-Socratic philosophers and the ones from Socrates’ time.
Roughly we can also say the ancient Greek philosophers ( the Pre-Socratic included) were composed of the men who were more interested in the physical sciences like Thales, Pythagoras, Aristotle, Democritus, Euclid etc. and the ones who prefer ideas, concepts, rhetoric, metaphysics like Parmenides, Socrates, Plato, Heraclitus, Xenophanes, the Sophists, Zeno, the Stoics, the Skeptics. The ones with a more “scientific” propensity seemed to work harder than the “metaphysical”, rhetorical ones. And they were interested in proof more than speculation. At their times, the second group were usually more numerous than the first. For some statistics in the present, the number of U.S. ( and probably much the same in Europe and Asia) college students enrolled in the hard sciences like math ( some view math more like an art), physics, chemistry, and engineering, are three or four time smaller than the students in the social sciences, and other majors together. And proving something in the physical “sciences” in their times, and similarly in our time, with evidences is a lot more difficult than just mere speculation.
Thales belonged to the first group. He, in reality, appeared to be substantially more practical also. We can point out some facts to support this more practical point.
From Socrates, who led the pack to turn to another direction of inquiry with more emphasis on the exact, on reasoning, the philosophers tried to improve their “art”. As such , before Socrates, Thales had figured impressively as one who had been ahead of his time for about 100-150 years, or around 4-6 generations.