It is perfectly clear that the fact these things share a single designation does not make one of them identical to the other. Thus, the very being of this existent (1) is not the very being of that existent, nor is the entity of this body the entity of that body, nor is the animality—or the humanity—of this living being identical to that of another. Rather, every existent, whether a man, a horse, or anything else, possesses within itself that by which it is distinguished from the rest of beings. A particular human being has a humanity that is unique to him, an animality that is unique to him, a corporeality that is unique to him, and an existence that is unique to him. It is these particular features that set him apart from everything else. Should he be supposed to pass away, those determinate qualities inhering in him pass away with him, yet it does not follow that his counterpart who shares those generic traits must also cease to exist. Once a numerically single, concrete individual is annihilated in itself, it is simply no longer there.
Everyone knows, by direct sense perception and by self-evident reason, that he is not that other human being, and that the attributes and accidents residing in him are not the very same as those residing in the other, even though he and that person share in humanity, rationality, animality, sentience, corporeality, substantiality, existence, essence, reality, and the like—everything that is said to be common between them.
Yet despite this sharing, neither of them is the other, nor is any attribute of one identical to the attributes of the other. In external reality there is no single concrete thing that they jointly possess; they merely resemble, correspond, and agree with one another in those notions. This is a fundamental principle that the discerning ought to know and master, for—despite its clarity, its obviousness, and its being among the self-evident, certain kinds of knowledge that admit no doubt—it has nevertheless confounded groups of learned people, so that they failed to distinguish between the one and the other.