Thales

Early Life and Background

Thales was born around 624 BCE in Miletus, one of the most prosperous Greek city-states on the coast of Ionia (modern-day western Turkey). Ancient sources, including Herodotus and Diogenes Laërtius, record varying accounts of his ancestry — some claiming Phoenician descent, others identifying him as thoroughly Milesian. Miletus at this time was a major center of trade and cultural exchange between the Greek, Egyptian, and Mesopotamian worlds, a cosmopolitan context that profoundly shaped Thales' intellectual horizon.

Travels and Education

Ancient tradition holds that Thales traveled to Egypt, where he studied geometry with the priests and learned techniques of land measurement that had been developed over millennia for surveying the Nile's floodplain. Proclus, following Eudemus of Rhodes, credits Thales with bringing geometry to Greece and with several specific theorems, including the proof that a circle is bisected by its diameter and that the base angles of an isosceles triangle are equal. Whether he traveled to Babylon as well is debated, but his astronomical knowledge suggests some familiarity with Mesopotamian observational records.

The Water Thesis and Natural Philosophy

Thales' most celebrated philosophical contribution is his assertion that water is the archē — the origin, substrate, and principle of all things. Aristotle, our primary source for this doctrine, interprets Thales as claiming both that water is the material out of which everything originally came into being and that it is the persisting substance underlying all change. The reasoning behind this choice is not preserved with certainty, but Aristotle speculates that Thales may have observed that moisture is essential to all life, that seeds are moist, and that nourishment universally contains water.

What makes this proposal genuinely revolutionary is not the specific choice of water but the form of the explanation itself. By positing a single natural substance as the ground of all reality, Thales broke decisively with mythological cosmogonies — the Hesiodic tradition that explained the world's origin through the genealogies and conflicts of the gods. He inaugurated a new mode of inquiry: seeking impersonal, rational principles behind the apparent diversity of nature.

Hylozoism: "All Things Are Full of Gods"

Aristotle attributes to Thales the enigmatic claim that "all things are full of gods" (panta plērē theōn) and reports that Thales held the magnet to have a soul (psychē) because it causes iron to move. This has been interpreted as a form of hylozoism — the view that matter itself is alive or animated. Rather than contradicting his naturalism, this doctrine may represent Thales' attempt to explain motion and change within nature without resorting to external supernatural agents. If the principle of motion (soul) pervades all matter, then nature's dynamism requires no external mover.

Practical and Scientific Achievements

Beyond his philosophical speculations, Thales was renowned for practical wisdom. The most famous anecdote concerns his prediction of a solar eclipse, which Herodotus dates to 585 BCE and which modern astronomers have confirmed. This prediction — likely based on Babylonian eclipse cycles (the Saros cycle) rather than any theoretical understanding of celestial mechanics — nonetheless cemented Thales' reputation as a sage.

Other stories illustrate his versatility: Aristotle tells how Thales, tired of being mocked for the impracticality of philosophy, used his meteorological knowledge to predict a bumper olive harvest, cornered the market on olive presses, and made a fortune — proving that philosophers could be rich if they wished but had higher priorities. He is also credited with practical feats of engineering, such as diverting the river Halys for King Croesus' army.

Legacy

Thales' immediate legacy was the Milesian school — his student Anaximander and grand-student Anaximenes continued the search for the archē, proposing the apeiron (the boundless) and air respectively. More broadly, Thales stands at the very origin of the Western philosophical and scientific traditions. His insistence on rational, naturalistic explanation set the agenda for all subsequent Greek philosophy and, ultimately, for the development of natural science. Aristotle himself acknowledged Thales as the founder of natural philosophy (physikē philosophia).

Thales died around 546 BCE. No writings survive, and his doctrines are known entirely through later testimonia, principally those of Aristotle, Diogenes Laërtius, and the doxographic tradition.