Aristotle 384-322BC
Greek philosopher and scientist, a highly important and influential figure in the history of Western thought

Aristotle was born at Stagira, a Greek colony on the pen-insula of Chalcidice. His father was court physician to Amyntas III of Macedon (grandfather of Alexander the Great). In 367 he went to Athens and was first a pupil then a teacher at Plato's Academy, where he stayed for 20 years until Plato's death in 347. Speusippus succeeded Plato as head of the Academy, and Aristotle left Athens for 12 years. He spent time at Atarneus in Asia Minor (where he married), at Mytilene, and in about 342 was appointed by Philip II, King of Macedon, to act as tutor to his 13-year-old son Alexander.

Aristotle finally returned to Athens in 335 to found his own school (called the Lyceum from its proximity to the temple of Apollo Lyceius), where he taught for the next 12 years. His followers became known as 'peripatetics', supposedly from his restless habit of walking up and down while lecturing. When Alexander the Great died in 323 there was a strong anti-Macedonian reaction in Athens; Aristotle was accused of impiety and, perhaps with the fate of Socrates in mind, he took refuge at Chalcis in Euboea, where he died the next year.

Aristotle's writings represent a vast output covering many fields of knowledge: logic, metaphysics, ethics, politics, rhetoric, poetry, biology, zoology, physics and psychology. He believed that sense perception is the only means of human knowledge. In ethics, he believed that human happiness is achieved by living in conformity with nature. In natural philosophy, he saw that the Earth is the centre of the eternal universe. He taught that everything beneath the orbit of the Moon was composed of earth, air, fire and water; everything above the orbit of the Moon was composed of ether. All material things could be analysed in terms of their matter and their form, and form constituted their essence.

Bibliography: Most of the extant work consists of unpublished material in the form of lecture notes or students' textbooks, which were edited and published by Andronicus of Rhodes in the middle of the 1st century BC. His work exerted an enormous influence on medieval philosophy (especially through St Thomas Aquinas), Islamic philosophy (especially through Averro�s), and on the whole western intellectual and scientific tradition. The works most read today include the Metaphysics (the book written 'after the Physics'), Nicomachean Ethics, Politics, Poetics, the De Anima and the Organon (treatises on logic).