Thomism

For six centuries after his death, Thomas Aquinas was one respected scholastic voice among several, read alongside Bonaventure, Duns Scotus and Ockham rather than above them. Thomism as a distinct, self conscious school is largely a nineteenth century creation, and the document that made it one has a name and a date. In 1879 Pope Leo XIII issued the encyclical Aeterni Patris, calling on Catholic education to return to Aquinas as its philosophical foundation against what the encyclical treated as the errors of modern thought since Descartes. The result was the Leonine edition of Aquinas's complete works, a wave of seminary curricula built around his Summa Theologiae, and a twentieth century revival that produced philosophers of real standing in their own right rather than mere commentators.

What survived the revival is a recognizable set of commitments rather than a museum piece. Thomism holds that existence and essence are really distinct in every created thing and identical only in God, that the intellect can demonstrate God's existence from the created order without appeal to revelation, and that natural law provides a standard of right and wrong accessible to reason alone. Those commitments still organize Catholic moral theology and much of Catholic philosophy of religion today, which is why Thomism remains distinguishable from scholasticism in general: it is one particular current within a much wider medieval movement, promoted to official status by a decision the wider movement never received.

Thomism's central grammatical problem is how any word applied to both God and creatures can mean anything coherent at all. If wise means exactly the same thing said of a human being and said of God, univocal predication, then God is simply a very large instance of a category creatures also belong to, flattening the difference Thomism insists on between an infinite creator and a finite creation. If the word means something entirely unrelated in each case, equivocal predication, then nothing true is actually being said about God at all, and theology collapses into silence. Aquinas's answer, analogical predication, holds a middle position: wisdom said of God names a real perfection possessed in a manner appropriate to infinite, uncaused being, and the same word said of a human names a related but genuinely different way of possessing a similar perfection, related by a real proportion rather than by simple sameness or sheer unrelatedness. The doctrine does real work beyond semantics. It licenses Aquinas's Five Ways, the arguments from motion, causation, contingency, gradation and design that reason from features of the created order to a creator, since those arguments depend on cause and effect sharing something real in common without the effect being simply a smaller copy of the cause. Later Thomists, Cajetan most influentially in the sixteenth century, spent lifetimes working out how analogy avoids collapsing into either position it sits between, a technical dispute that never fully closed.