(On abstraction, the first part of something)
The theory of abstraction is opposed to various theories of innate ideas. The strongest justification of the theory is that various physical calamities and misfortunes deprive us of ideas: being born without vision leaves one with no ideas of colors; and getting beat over the head, being sick, or being drugged make it harder to form ideas. But it is important to be precise about just what the argument proves: namely that our object of thought is necessarily conditioned by sense, and that the sensible as such is a necessary element in it. A comparison to the will is helpful: although the freedom of the will is real and as such must always transcend the necessity or probability of physical law, this freedom always expresses itself through a latticework of physical necessity of probability. The unity of body and soul gives a puzzling unity to all of its operations: any choice it makes is a puzzling melange of freedom and necessity and any object it understands is an equally puzzling melange of physical and non-physical cognitive powers. Say I look out my window and see a parking lot. Is that an object of sense? I have a sense for colors and shapes, and I even have sensible powers to associate some colors and shapes with others and make a more or less analogous image to other things. But I have no parking lot sense; no sense power for detecting artifacts. If I showed a great ape a picture of a parking lot in another galaxy, I doubt it would register any reaction at all – but if I showed it to even a junior high kid, they would be absolutely amazed. So I can perceive “black/stationary/white lines every ten feet” and I can perceive “artifact”. So which one is, well, out there? There is no avoiding speaking about the object “out there”, but it cannot be the case that the sensible object is “out there” while the intelligible object is not.
On Aristotle’s account of things, “black” is a sensible per se and “artifact” is sensible per accidens. This is fine, but the per accidens sensibility in question reduces to a double perseity: on the one hand it reduces materially to the per se sensible, but on the other hand it reduces formally to the per se intelligible. This is crucial to point out, for many accounts of abstraction seem to be at least tacitly assuming that our per accidens sensible objects reduce only to what is given per se to sensation. This, in fact, commits the exact same error that St. Thomas critiques in Plato: just as we have no pure intuition of a intelligible species, so too we have no object that is purely and simply per se sensible. All our reds are red things; all our mobiles are mobile subjects; all our numbers are countable species. The axiom nihil in intellectu non prius in sensu cannot be taken as meaning that we have some “pure sense intuition” that becomes a phantasm that subsequently and within the limits of the soul has intelligibility added to it. We no more have pure sense intuitions than innate species.
Aliter: consider the standard account of the proper object of human cognition: the quiddity of sensible things. This is fine, but quiddity is only sensible per accidens, and so we are saying the object is what is not sensible per se in what is sensible per se. So is the proper object of the human intellect sensible or not? The question is ridiculous, like asking whether man is soul or body.