Aristotle, 384-322 B.C., Greek philosopher. He studied (367-347 B.C.) under Plato and later (342-339 B.C.) tutored ALEXANDER THE GREAT at the Macedonian court. In 335 B.C. he opened a school in the Athenian Lyceum. During the anti-Macedonian agitation after Alexander's death Aristotle fled (323 B.C.) to Chalcis, where he died. His extant writings, largely in the form of lecture notes made by his students, include the Organum (treatises on logic); Physics; Metaphysics; De Anima [on the soul]; Nicomachean Ethics. and Eudemian Ethics; Politics; De Poetica; Rhetoric; and works on biology and physics. Aristotle held philosophy to be the discerning, through the use of systematic LOGIC as expressed in SYLLOGISMS, of the self-evident, changeless first principles that form the basis of all knowledge. He taught that knowledge of a thing requires an inquiry into causality and that the "final cause" -- the purpose or function of the thing -- is primary. The highest good for the individual is the complete exercise of the specifically human function of rationality. In contrast to the Platonic belief that a concrete reality partakes of a form but does not embody it, the Aristotelian system holds that, with the exception of the Prime Mover (God), form has no separate existence but is immanent in matter. Aristotle's work was lost following the decline of Rome but was reintroduced to the West through the work of Arab and Jewish scholars, becoming the basis of medieval scholasticism.