Make logic possible? How is that a coherent idea? Logic is necessary. With the universal there can be no question of whether “it is” or “is not.” Universals are always true.
Aristotle is the one who doesn’t believe in the universal here. He is the one who says, in response to me telling him that it’s necessarily true that a tree means tree, that I’m talking nonsense unless I suppose some specific force of the world which makes logic true, as if the tree began without the meaning of tree. Logic supposedly isn’t enough on it’s own. Logic is thought be defined by
states of the world or else fall into incoherence.
This is why Aristotle understands the world to be defined by general categories. To fill the supposed “gap” he relies on observed states of the world. On observing an human, he sets out a standard which supposedly tells us when human are present. We can supposedly tell when a human is present by these “general, universal properties” which define the existence of a human.
But this creates a problem. Now there is a restrictive standard. At what point does a thing qualify as human? What if it’s missing an arm? A leg? Certain states of consciousness? Or what if someone has an extra finger, limb or hair? If these “general universal properties” were to define the meaning they would have perfectly account for the meaning of
any possible human. Clearly, this is untrue. Many possible humans do not fit these meanings.
Aristotle is a
reductionist who eliminates the meaning expressed by many states just to get the (supposedly) “universal truth” which describes everything in one moment. Like the person saying “consciousness” is just a brain, Aristotle equivocates a vast array or states and the meaning they expressed with something else entirely.
Thinking is not an abstracting process. It is a specifying one. Each thought picks out one specific meaning, one which is no other, a universal. For metaphysics to be more general or vague destroys this. What are unique expressions of meaning get reduced to the presence of some other thought— “Humans are necessarily X,Y,Z ”, “Experiences are brains.”
The sort of inference you are talking about is reductionism. Supposedly, by having one thought (humans, experiences) we must mean another (X,Y,Z, brains) and there's is no room for these meanings to occur on their own terms.
In terms of metaphysics, one could not get more wrong. It’s the equivocation of the order of the empirical with the logical, which goes both ways. We end up in the absurd situation where the logical is read as empirical (a caused truth, the meaning of properties X,Y,Z=existing humans, the meaning of experiences=existing brains, etc.,etc.) and empirical is read as logical (supposedly, empirical states are necessarily by logic: first cause, PSR, God, "constrained by the universal,"etc.,etc.). For these metaphysics, "vagueness" is a requirement because the universal nature of every logical truth is rejected. For them any truth is "vague" because is it has to have its logical meaning given by a different meaning.