Philosophy is defined as an organized system of thought that comes from the Greek term meaning "love of wisdom." The document discusses several influential ancient Greek philosophers and historians including Socrates, Plato, Aristotle, Herodotus, Thucydides, Eratosthenes, and Euclid. Socrates developed the Socratic method of questioning and taught philosophy for no pay. Plato was a student of Socrates and wrote down his teachings. Aristotle had wide-ranging interests and studied many subjects. Herodotus and Thucydides are regarded as the earliest historians in Western civilization. Eratosthenes calculated the circumference of the Earth. Euclid wrote a geometry textbook still used today.