Thales of Miletus

Thales lived in Miletus on the Ionian coast around the turn of the seventh to sixth century BC, counted among the Seven Sages of early Greece. He proposed that a single substance underlies all nature and settled on water, theorizing the Earth itself floated on it. The shift mattered more than the answer: he reached for natural philosophy where predecessors had used mythology, earning him retrospective billing as the first philosopher and the first to attempt mathematics and deductive reasoning in the Greek line. He calculated pyramid heights, predicted weather and a solar eclipse, charted Ursa Major and the solstices, and engineered a river crossing for the Lydian army. Plutarch later wrote that Thales alone had lifted philosophy from speculation into practice.