Aquinas, St Thomas
Aquinas, St Thomas (1225-74), Italian Catholic philosopher and theologian. He became a Dominican friar in 1243, against the wishes of his family, who imprisoned him for two years. After escaping to Cologne, where he studied under Albertus Magnus, he taught in Cologne, Paris, and Rome. His writings, especially the complete theological system attempted in the Summa Theologiae, continue to exert enormous influence.