Tommaso d'Aquino, OP (1225–74), known as Saint Thomas Aquinas, is a Doctor of the Church. He was an Italian Dominican friar and Roman Catholic priest, who was an immensely influential philosopher and theologian. His influence on Western thought is considerable, and much of modern philosophy developed or opposed his ideas, particularly in the areas of ethics, natural law, metaphysics, and political theory. The works for which he is best known are the Summa Theologiæ and the Summa contra Gentiles. The Catholic Church honors Thomas Aquinas as a saint and regards him as the model teacher for those studying for the priesthood.
Thomism is the theology of Thomas Aquinas or of his followers.