Thomism

Thomism is the philosophical and theological system of Thomas Aquinas, the thirteenth-century Dominican friar whose Summa Theologica, begun around 1265, produced the most systematic medieval synthesis of Aristotelian philosophy with Christian theology, arguing that reason and revelation, rightly understood, cannot conflict because both ultimately proceed from the same divine source of truth. Aquinas adapted Aristotle's metaphysics of substance, potentiality and actuality, and his theory of causation to construct five philosophical arguments (the "Five Ways") for God's existence from observed features of the world, such as motion, causation and the graded perfection of things, while distinguishing what reason can establish about God unaided from truths, such as the Trinity, accessible only through revelation. His natural law ethics holds that human reason can discern objective moral principles, rooted in human nature's orientation toward its proper ends, that bind independently of positive religious law, a framework that became foundational for later Catholic moral and political philosophy. Though briefly overshadowed after Aquinas's death by rival Scholastic currents, including Scotism and nominalism, Thomism was revived and made the official philosophical framework of Roman Catholic teaching by Pope Leo XIII's 1879 encyclical Aeterni Patris, and Thomistic philosophy remains an active tradition in contemporary Catholic and analytic philosophy alike.