(presumably that of May 28, 585 BC). If these accounts are accurate, they point to a familiarity on Thales’
part both with Egyptian surveying techniques and with Babylonian records of celestial phenomena.
Thales’ most impressive accomplishment, however, was in the field of philosophy, of which he may be
said to be the founder. None of Thales’ writings has survived; nor do we even know for sure that he put
any of his ideas into written form. We are told, however, that he claimed that the earth is supported by
water, like a floating piece of wood, and that, indeed, water is the ultimate and original substance of
everything that exists. These claims bear some similarity to earlier Egyptian, Babylonian, and Hebrew
accounts of the origin of the universe (compare “and darkness was upon the face of the deep” from the
opening of the book of Genesis). But, in these essentially mythical accounts, either the primordial waters
are personified as deities, as when Homer refers to “Ocean, the source of the gods,” or they are part of
the raw material from which a creator-god crafts the world as it is now. Thales seems to have divested
his own propositions of any mythical elements. Now this, of itself, is not necessarily either a
philosophical or a scientific development, but its consequence is both. For, while different, and even
incompatible, mythical accounts often happily co-exist, an assertion like that of Thales can only either be
accepted as a valid explanation or challenged and replaced by a more satisfactory account.
“When Croesus reached the Halys River, what happened next, as far as I can tell, is that he got his
army across the river using the already existing bridges. According to the prevailing account among
the Greeks, however, it was Thales of Miletus who managed to get his army across for him. For they
say that, when Croesus was unable to figure out a way for his army to cross the river (since,
supposedly, the aforementioned bridges did not yet exist at that time), Thales, who was in the camp
with the army, got the river to flow to the right of his army as well as in its regular course to the left.
This is how he did it: Beginning at a point upriver of the camp he had a deep trench dug, directing
that it curve around so as to flow behind the place where they had pitched camp. In this way he used
the trench to divert the river from its old course and then, when it passed around the camp, to return
to its original bed, so that the river became fordable in both places as soon as it was divided in
two.” (Herodotus 1.75.3–5)Thales’ assertion did not have to wait long to be challenged. In fact, it was another Milesian, Thales’
younger contemporary Anaximander, who propounded a rival theory. According to Anaximander, it is not
water that is the basic element of the universe; rather, it is something that Anaximander called “the
indefinite” or “the infinite.” Anaximander even attempted to account (in the one brief fragment of his
actual wording that we possess) for the perpetual process of change that the universe undergoes, in terms
of the “compulsory penalty” that entities pay for wrongfully encroaching upon one another; in this way the
alternation of night and day, of hot and cold seasons, of periods of rain and drought, could be explained in
terms of a “natural” balancing out of contrary properties. Anaximander’s theory was itself subjected to
encroachment by yet another Milesian, a younger contemporary named Anaximenes, who proposed that
the fundamental substance of the universe was neither water nor “the indefinite” but air. Anaximenes, too,
attempted to explain change in the universe by appealing to the processes of condensation and rarefaction,
by which air can become water and fire and, according to Anaximenes, everything that is found in the
universe.
It is perhaps not surprising that Miletus was the birthplace of philosophy and of scientific inquiry as we
know it. Like other Ionian cities on the coast of Asia Minor, Miletus prospered during the seventh and
sixth centuries and its citizens had relatively easy access to the sophisticated civilizations of Egypt and
western Asia. Unlike the other Greek cities on the coast, however, Miletus had managed to maintain its