One Argument for Matter as the Principle of Individuation

1.Material substances that are of the same species are numerically multiple.

2.This multiplicity must have its source in one of the general principles of material substances.

3.Since species is formal, this formality must then be multiplied either according to itself or according to something else.

4.If it is multiplied according to itself, then we would have distinct formalities by which something is made a member of a species.

5.To have distinct formalities, though, is to have different species. Different forms cannot constitute identical objects.

6.Therefore form cannot be the cause of numerical division in species.

7.The formality, then, must be multiplied according to something else.

8.We are left with matter, or the subject into which the substantial form is received.

9.Therefore matter is the principle by which members of the same species are individuated.


Three, then Two

Inasmuch as we consider the principles of mobile being as constituting the object in its becoming, we have three principles, two of which are opposed to one another.


To become something else, even in an accidental way, is to assume some new form and lose the previous one. The privation is the form-from-which and the form, simply, is the form-to-which. The subject (matter) is named so because it is the subject of these forms in its changing and static state.

When we consider the principles of an object as it is in act, meaning in actual existence, then we are left with two principles, form and matter. This is the hylemorphic conception of material substances. Form and matter are not opposed to one another since opposition cannot, of itself, produce unity, and the object, as one object, is necessarily unified. Therefore its principles, considered as constituting the actual object, cannot possibly be opposed to one another or contrary to one another.