Thales of Miletus

In 585 BC, a scientist and philosopher in the Greek city of Miletus offered a bold prediction: On May 28 of that year, he said, there would be a total eclipse of the sun. Such predictions, based on previous astronomical observations, were virtually unheard of in the ancient world. Few people in the Greek world believed that celestial events like eclipses could be foreseen; instead, they ascribed them to all-powerful gods. But the Miletian scientist, Thales (620– 546 BC), stood by his claim that human reason alone could be used to predict nature.

And indeed, on that day, a swath of what’s now Turkey was cast into total darkness, just as Thales had prophesied. The eclipse terrified the Miletians, vindicated Thales—and, arguably, set in motion the history of Western science. Prior to Thales, most Greeks considered religion and nature inseparable. Events like earthquakes and eclipses, they believed, happened when angry gods wanted to send a message to  mankind. Greek mythology abounded with stories of the deities directly intervening on Earth. By correctly predicting an eclipse, however, Thales profoundly altered the Greeks’ understanding of nature and of the value of knowledge. He also created the concept of philosophy—derived from the Greek words for “love of wisdom”—to describe those who sought to use reason to understand the world. Thales was a trader and olive oil producer who had traveled to Egypt, where Miletus had a trading outpost, and to the Near East. He may also have traveled to Babylon, where he could have learned the Babylonian astronomical concepts that enabled him to predict the eclipse.

When he returned to Miletus, Thales founded a school of philosophy that would train several important Greek thinkers, including Anaximander (c. 610–c. 546 BC) and Anaximenes (585–525 BC). In addition to his scientific and philosophical work, Thales was a military advisor to several kings and played a role in preserving Miletian independence after the Persians defeated neighboring Lydia.

His death came suddenly at about age sixty—he supposedly dropped dead while watching a gymnastics performance.


  1. Thales believed that the world was made of water and that all forms of matter had started as water.
  2. The site of ancient Miletus is now the city of Milet, Turkey.
  3. According to one story, Thales once traveled to Egypt to study Egyptian geometry. He supposedly dazzled his hosts by correctly calculating the height of a pyramid based on the length of its shadow

Share this Post