Aristotle, a student of Plato, is universally considered as one of the great thinkers of the ancient world. His father was the personal physician to the King of Macedonia, and eventually Aristotle would become a tutor for that King's grandson, Alexander the Great. While still in his teens, moved to Athens to attend Plato's Academy. He studied with Plato for twenty years, until Plato's death in 347 BC. Aristotle known as a brilliant student, and he had hopes of taking over the Academy after Plato's death. For a number of reasons, however, this did not occur. Aristotle left Athens and traveled for several years in the Greek Islands and the Middle East. Aristotle then accepted an indication from the King of Macedonia to tutor the King's son, Alexander. After the King of Macedonia was assassinated and Alexander ascended to the throne, Aristotle returned to Athens and began his own school, known as the Lyceum.
There, he lectured while walking, and became known as "The Peripatetic", which means "to walk about" in Greek.
Aristotle lectured for twelve years on numerous subjects, including the plants and animals of the natural world, logic, physics, ethics, politics, and metaphysics. These lectures were to influence western thought for thousands of years. Aristotle eventually had to flee Athens, fearing for his life. It is claimed that Aristotle claimed that he should leave Athens, to prevent it from sinning against philosophy a second time. Aristotle's writings exercise a tremendous influence over western thought, and was so highly regarded that he was often simply referred to as "The Philosopher" by later writers.