As near as I understand the question, let me answer with a bit of historical narrative.
Peter Abailard was interested in the question of universals. His definition was that it is the kind of thing that can be predicated to many things (e.g., man - man is a universal because it can be applied to every man). Given the logical definition, he went on to ask the nature of universals (n.b., this is not a question for logic, but for philosophy). His logic professor (William of Champeaux) was something of a realist. That is, universals were not merely concepts of the mind, but real things--substances--found in things. Plato and Socrates are both men precisely because there is something in common between them: their humanity, and this humanity must be just as real as any thing else we really talk about.
Abailard pointed out the fallacy in that perspective immediately, which I think goes a long way in answering your friend's question. If human nature is a real thing--a substance--that is present in both men, then it is only partly present in both men; but if it is only partly present, then neither man is truly man, but only partially man. If humanity is entirely present in one, though, it cannot be present at all in another, which would make one a man and not the other. He was right thus far, but then he took a wrong step: if humanity can neither be partly nor completely found in any man, then it is not something; and that which is not something is nothing.
Now William tried to find a middle ground for his position, but ultimately failed for the reason that all strict realists must fail. Abailard's argument was correct, insofar as it went. Universals cannot be real substances, for if they are--as real things--they are either in things wholly or partly; if wholly, they are in nothing else, and if partly, then the thing in which they are found are not fully that thing. But that would prove no comfort to Abailard. For his own view was equally flawed. For if "humanity" is really nothing at all, then there is nothing
in a man that corresponds with our word "man." Thus, we see Abailard's reasoning fail for the same reason all nominalism fails -- if there is nothing real (in some sense) corresponding to our words, then our words have no real meaning. In other words, having proven universals are not substances, Abailard had to show how we could justifiably attribute them to things if they do not really exist at all--that is, if there is nothing in the thing to which we are attributing them to which they can correspond. He failed to accomplish his impossible task, precisely because he had not taken the road Aristotle did.
So perhaps Aristotle wasn't a novice missing such things after all . . .
Or perhaps I've completely misunderstood your question, and as such, would point you to the better educated Aristotelians that hang around here.