The Cave and the Light: Plato Versus Aristotle, and the Struggle for the Soul of Western Civilization

by Arthur Herman

Aristarchus’s heliocentric theory was an astonishing leap into the future. However, it found no buyers among other Hellenistic astronomers. They took a straightforward geometric, rather than dynamic, view of motion. As orthodox Aristotelians, they couldn’t understand the idea of force or acceleration except in terms of something pushing something else (it will take Galileo and Newton to set that issue straight). Nor could they understand why, if the earth really did rotate, everything not tied down or rooted in the ground did not eventually fly off in the opposite direction.10 It’s not known how Aristarchus answered what, given the assumptions of the time, were reasonable objections backed by the authority of Aristotle himself, or even if he did. In the end, Greek astronomers preferred to stick to Aristotle’s “celestial spheres” to explain the movement of the planets and the stars.‡ The earth remained the center of the universe for another two thousand years. Even so, the mathematical computations of Alexandrian astronomy remained at a very high level. The philosopher of mathematics Bertrand Russell has called them “works of astonishing genius.”11 This amazing—if ultimately misleading—work culminated in the treatises of the great Ptolemy (no relation to the ruling dynasty) in the first century CE. Ptolemaic astronomy was Alexandria’s last word on the geocentric view of the cosmos. It would remain Europe’s principal guide to astronomy until the Renaissance. Ptolemy’s greate...