In the "Phaedo," Plato's Socrates seems to be saying that the forms are causally responsible for their instances, and he seems to be saying similar things in the "Meno." In the past it was common to say that forms explain their instances, rather than causing them to be. More recently, scholars began urging us to take Socrates more literally. I side with them while insisting that causation by participation in form must be a spatiotemporal affair, rather than a mysterious relation between transcendent and sensible reality. This leads me to develop an account of forms that distinguishes between their roles as intelligibles, and as immanent causal powers, with surprising implications for Plato’s epistemology. Most notably, I argue that Plato’s admission of forms into the sensible world as causal powers casts doubt on his commitment to innate knowledge (i.e., the theory of recollection).