Thomas Aquinas

Thomas was born to a noble family near Naples and sent at five to the abbey of Monte Cassino, which the family expected him to rule one day. At the University of Naples he met Aristotle and the new Dominican order, and at nineteen chose to join the mendicant friars. His outraged family kidnapped him and held him at home for a year; they are said to have sent a prostitute to tempt him, whom he drove out with a firebrand.

Released, he studied under Albert the Great in Paris and Cologne. Fellow students called the silent, heavy young man 'the dumb ox'; Albert said the ox's bellowing would be heard around the world. He taught twice at Paris and in between at the papal court in Italy, dictating several works at once, reportedly to different secretaries simultaneously. In December 1273 something happened to him during Mass, after which he refused to write, saying that compared with what he had seen everything he had written was straw. Summoned to the Council of Lyon the next year, he died on the road.

The Summa Theologiae, unfinished, still contains over three thousand articles, each stating objections, citing an authority, answering and then replying to every objection. His central theme is the harmony of nature and grace: reason can prove God's existence (the Five Ways) and much else, revelation supplies what reason cannot reach, and the two never conflict. From Aristotle he took potency and act, matter and form; from Avicenna the distinction of essence and existence; and he built a hierarchical universe in which everything is ordered to God. Canonised in 1323, he was declared in 1879 the official foundation of Catholic philosophy.