An Argument for Substantial Form

I provide an argument, based on Thomistic principles, for substantial form, understood as the single principle of substantial actuality for any natural substance. To make this argument, I distinguish between substance and accident, between the natural and the artificial, and between ontological and methodological reduction. I respond to two objections to the Thomistic doctrine of substantial form raised by Benjamin Hill: I explain how it is possible for Thomas to account for the presence of elements in compounds and also to account for the fact of natural instances that fail to realize the full reality of the substantial form ("monsters").