Thales of Miletus (c.624-c.546 BC). 1887 illustration of a bust of the Ancient Greek philosopher and one of the Seven Sages of Greece Thales. Thales lived at Miletus, an Ionian Greek city in what is now Turkey. He was a pre-Socratic philosopher, regarded by many (including Aristotle) as the first in the Greek tradition and thus of Western thought. He was the first to attempt to explain natural phenomena without recourse to mythology. His use of deductive reasoning, establishing general principles and formulating hypotheses is the basis of modern science. He was the first person to apply deductive reasoning to geometry and is considered the first true mathematician.