Abstract

Bringing together two aspects of Thomas Aquinas's thought that have been studied separately: his theory of God's concurrence and his theory of instrumental causality, I show how he uses the latter (which I discuss first) to clarify the Proclusian principle that the first cause has a greater influence on an effect than the proximate causes. Thanks to this theory, Aquinas accounts for the fact that it is God who confers existence to every new being that is produced by natural processes, without however negating the agency of secondary, created causes.