Aristotle, born at Stagira in Thrace about 384 B.C., by inheritance and early training had a strong bent toward natural science, since he was descended from a line of physicians who, according to Galen, taught anatomy by dissection. For twenty years he was the pupil and assistant of Plato in the Academy. After the death of his master he went to the court of Hermias, a prince of Mysia, and in 343 he was appointed tutor to the son of King Philip of Macedon, Alexander, then thirteen years of age. About 335 he opened a school in the Lyceum at Athens, where he taught for some thirteen years. Then, being accused of impiety after Alexander’s death, he withdrew to Chalcis in Euboea, as he said, that the Athenians might not sin a second time against philosophy; there he died about 322. Into Aristotle’s encyclopedic knowledge and enormous scientific activities we may not now go; and indeed we need not dwell at very great length upon him, for his influence in religion was less potent than Plato’s through antiquity and the earlier Middle Ages. The chief cause of the elder philosopher’s greater influence is to be found in the fact that Plato’s thought centered on man, his morality, and his relation to God, while Aristotle was concerned primarily with the universe of which man was to him only a part; to Plato virtue was inseparably connected with religion, and was therefore something to be sought with fervent spirit as well as with cool reason; to Aristotle virtue was rather an intellectual matter, an even balance of the soul, that natural perfection of the whole organism on which the well-being and happiness of man depended—a state which was to be attained by right calculation, choice, and habit. So it came to pass that although Aristotle’s works on logic were continuously studied in one form or another, his great sway in many realms of human thought, including theology, began in the thirteenth century, when, learning first from Arabic scholars, later aided and stimulated by the Latin conquest of Constantinople in 1204, the western intellectual world eagerly studied his works anew. Then Albertus Magnus, St. Thomas Aquinas, and Roger Bacon raised him to the supreme position in philosophy and theology, so that he became for that age indeed “the master of those who know.”