Causes, principles and elements. Aristotle's strategy in Metaphyscs Z - H

Aristotle maintained that kind-membership is not a primitive fact about the world, but one which depends on the prior fact that some parcel of matter is shaped by a «form» or a functional set of capacities. These capacities enable the resulting composite to perform the proper operations of its species. So understood, the form works as a «principle», and not as an «element», of the composite. This paper attempts to clarify in which category of being, if any, Aristotelian forms belong. It argues that an Aristotelian formal principle ought not to be considered as a mere immanent variation of the Platonic eidos, which would differ from the latter only insofar as it dwells in the sublunary realm.