Thomas Aquinas 1225 – 1274

Thomas Aquinas was a 13th-century Italian Dominican friar and philosopher, the most influential figure of medieval scholasticism. His Summa Theologica, left unfinished at his death, is the most ambitious systematic synthesis of Aristotelian philosophy with Christian theology in the Western tradition. He developed five proofs for the existence of God, an integrated account of natural law and ethics, and detailed treatments of human action, virtue, and the sacraments. Aquinas was canonized in 1323 and named a Doctor of the Church; his thought was declared the standard Catholic philosophical and theological framework by Pope Leo XIII in 1879. The school of thought based on his work, Thomism, remains an active philosophical tradition.

Thomas Aquinas (1225–1274) was the most influential Christian philosopher of the high Middle Ages and the figure who completed the integration of Aristotle's recovered corpus into the Latin Christian tradition. Born to an aristocratic family in the Kingdom of Sicily, he entered the Dominican Order against his family's wishes — they imprisoned him for over a year in an attempt to dissuade him — and studied under Albert the Great in Cologne and Paris.

Aquinas's surviving body of work includes commentaries on most of Aristotle and on the major books of the Bible, philosophical treatises on disputed questions, and the two great theological summae. The Summa contra Gentiles (1259–1265) presents the rational case for Christian doctrine to non-Christian readers. The Summa Theologica (1265–1273) — left unfinished at Aquinas's death — is the comprehensive systematic theology that has structured Catholic philosophical theology ever since. The Five Ways for the existence of God, the analogical doctrine of divine attributes, the natural-law account of moral philosophy, and the integration of Aristotelian metaphysics with Christian doctrine are all among its central contributions.

Aquinas was canonized in 1323 and declared a Doctor of the Church in 1567. The Thomist tradition — in its medieval, Counter-Reformation, and twentieth-century neo-Thomist forms — has been one of the most continuously productive philosophical traditions in Western history. He died on the way to the Council of Lyon in 1274.