Monday, February 01, 2010

Thales and the Greek Enlightenment

I began reading Karl Popper last summer and it has been a valuable experience. I'm currently rereading his essays on the Presocratic philosophers for a lecture I give about the place of the Hippocratic writers in ancient Greek thought. Although (or perhaps precisely because) he was not a Classicist, Popper offered a number of revolutionary insights about early Greek philosophy and its role in western civilization. Those insights have been largely ignored by Classicists. His most exciting contribution, in my opinion, is his revaluation of Thales' impact on philosophy and science. If you ever read something about Thales, it is likely that he predicted an eclipse and thus began philosophy or science. This seems highly unlikely to me. Popper's argument runs like this.

It was common for both ancient philosophical schools and religions to organize around a single man who was considered a master or prophet. For pagan observers even the early Christian church fits this paradigm, as evidenced by Galen's use of the formulaic phrase "the followers of Moses and Christ." The schools were dedicated to learning the teachings of their master and spreading them to contemporaries and the next generation. There was typically no room for innovation; any new elements were painstakingly attributed to the master himself, so that the philosophy or doctrine would appear to have sprung from him perfected already. The real origin of western philosophy and science is found sometime in pre-classical Greece when a tradition of critical discussion was developed. What Popper sees with fresh eyes is that this development appears to have begun with Thales.

Thales hypothesized that the earth rested on a body of water. This explained the foundation of the earth, it explained why the earth was seemingly surrounded by "the river Ocean," and it also provided a convenient explanation for seismic activity. The question then arose: on what does the water rest? In order to avoid this problem of infinite regression, Anaximander, a student of Thales, suggested that the earth did not rest upon anything. Rather, he claimed, it hung pendant in space, and was held in place by its central position. It seems that Anaximander thought of the earth as a sphere, but in any case, the idea was current not much later. Within a few centuries not only was the notion of a spherical earth widely accepted, but its size was accurately calculated by Eratosthenes.

Although Thales was only about fourteen years older than Anaximander and they died around the same time, and were both active in the Milesian school, there is no ancient tradition about an intra-school feud. This suggests that Thales tolerated dissent from his students, and perhaps even encouraged it. Perhaps it seems trivial, and indeed it has been overlooked or unappreciated throughout history although it was right before our eyes, but I think Popper is right to see this as the great contribution of Thales and the proper mark of the origins of western science.