Beginning of Science
Before Thales [of Miletus], those seeking answers as to how or why things occurred in the universe invariably referred to the gods. Divine interventions caused earthquakes, changed the seasons, played with the lives and health of puny mortals, and so on ad infinitum. People had only a hazy idea of the shape of the earth and the surrounding cosmos. Many believed the earth was flat and round, floating boatlike on an all-encircling ocean. They then added to the disk of earth sitting in its ocean-saucer some form of pillars or supports (the Egyptians placed them at the cardinal points and anthropomorphized them as the arms and legs of the sky goddess Nut), holding up the dome of the heavenly firmament which sun, moon, and stars traversed in a regular manner. Outside this cosmic eggshell some placed water, which could descend from above in the form of rain and snow or well up from below in springs, lakes, and wells. But what was all this actually composed of? What was the fundamental matter? Before Thales, and for many after him, the answer to this question was invariably divinity. Call it soul, spirit, or god, the fundamental matter was divine, untouchable, metaphysical.
Thales, however, preferred water. Water is, after all, fundamental: It can be solid, liquid, or gaseous, and without it there can be no life. Right up until the nineteenth century [C.E.] scholars believed that life could generate itself spontaneously in water. As the early metallurgists had discovered, even metals could be reduced to liquids with sufficient heat. And with the seasonal inundations of the great rivers of the ancient world—the Nile, Tigris, and Euphrates—water created earth in revitalizing silt deposits and islands in the deltas of these great rivers.
But this is where Thales made his great leap. He asserted that earthquakes were the result of waves, disturbances in the water on which the earth floated, and not the acts of irate gods. This was one of the greatest revolutionary ideas of all time.
Of course today we know that earthquakes are not caused by ripples on a cosmic ocean, but it is Thales’ idea, not his conclusion, that matters. In attributing a natural phenomenon to mechanics and not gods, he took the universe out of the hands of divinities and claimed, extraordinarily, that everything was understandable, knowable. The furious sea god Poseidon was no longer shaking the planet as he strode across it. Something physical was making the world shake. This idea alone marks the beginnings of science.
— The Rise and Fall of Alexandria, pp. 96-97