susceptible to the action of causes—namely, matter—it cannot be individuated unless its nature is such that its species must exist as a single individual. But if the nature of its species admits of being predicated of many, each is individuated by a cause. Thus, there cannot in reality be two instances of blackness or two instances of whiteness unless they differ in their subject or in something serving the same function.”

He said: “If that by which it is individuated is incidental to the shared necessity, with this incidence resulting from a cause, then, if that cause and that by which the essence is individuated are one and the same—so that the cause of the incidence is the cause of the individuation—that cause would cause the particularity of that whose existence is necessary in itself. The essence of the Necessary Existent would therefore have a cause, which is impossible. If, however, its being incidental to the shared necessity occurs after an earlier individuation, then the argument applies to that earlier individuation.”

A fourth possibility remains: that what individuates each, distinguishing it from the other, is a necessary concomitant of what they share. This is impossible in every case, as explained above. Thus, the impossibility of two necessary existents is established, and necessary existence must entail individuation; its individuation is therefore due to its being the Necessary Existent