 The essence of such a hylomorphic compound is evidently its form, not its matter. As Aristotle says “by form I mean the essence of each thing and the primary substance” (1032b1), and “by the substance without matter I mean the essence” (1032b14). It is the form of a substance that makes it the kind of thing that it is, and hence it is form that satisfies the condition initially required for being the substance of something. The substance of a thing is its form.