‘The study of philosophy is that we may know not what men have thought, but what the truth of things is.’ Thomas Aquinas (c. 1225–74) was one of the most influential philosophers of the Middle Ages, and his works continue to be widely read today. The leading classical proponent of natural theology and the founder of Thomism, he is regarded as one of the greatest Western thinkers of all time. Written by a world authority, this brief history begins with an engaging account of Aquinas’s life and intellectual context. Thomas Aquinas goes on to explain the main contours of his thought for readers who may have no previous knowledge of him, or of academic philosophy and theology. It concludes with an informed assessment of the scale and significance of his legacy.