A thing is defined by its two elements, material difference within a form.
What we are, mind, is one of several environmental acquisition systems of a living organism. What makes anything what it is is determined by its definition. If you understand that a Set is determined in only one of two ways, enumeration and definition, you might be able to generalize Set, into Thing, and see that definition, and definition determines predication, or assertion and denial--the very basic sentence itself. So, is not form qua form, nor material qua material, but, as Aristotle pointed out, and as Plato pointed out, the combination of both. By definition also.
By definition, we as mind are that environmental acquisition system of a living organism which must acquire from things in the environment, forms to apply as human behavior that maintain and promote the life of the body.
Definition determines what we are.