According to ecological psychology, animals perceive not just the qualities of things in their environment, but their affordances: in James Gibson’s words, ’what things furnish, for good or ill’. I propose a metaphysics for affordances that fits into a contemporary anti-Humean metaphysics of powers or potentialities. The goal is to connect two debates, one in the philosophy of perception and one in metaphysics, that stand to gain much from each other.