Unity and Primary Substance for Aristotle

Primary substance for Aristotle is either the individual or form. These same two possibilities are the leading candidates for the source of unity in a substance.Thus, if we could determine what is responsible for the unity of a substance, we may well have located primary substance also. I consider the following possiblesources of the unity of form and matter in a substance:1) The unifier is a connector external to form and matter. (This connector may be itself a form, matter, or a relation that is neither formal nor material.)2) There is no need for a unifier because form and matter are simply conceptual ways of understanding a single, already-unified, concrete being.3) The unifier is an inherent aspect of form or matter.I proceed by a process of elimination and conclude that substantial form is both what unifies a substance and the better candidate for primary substance