Questions for Thomists Regarding Immaterial Intellects

I wrote the following to a colleague who teaches in my university's psychology department. I have retained the substance of my written correspondence to him:

Thomists argue that we need immaterial intellects to apprehend abstract universals. But how do we know that physical organs are only capable of apprehending concrete particulars? What incontrovertible proof do we have that intellects (of the Thomistic caliber) even exist? I admit that an intellect qua a power of the soul is logically possible (i.e. not self-contradictory). However, I am not convinced that such a faculty is factually possible (i.e. that it actually exists). So I guess my first line of attack would be to question the existence of the non-material intellect. Secondly, I would argue that what has been called "intellect" is really nothing more than a higher-order process of the brain: intellection is a biological phenomenon (see the work done by John Searle). The brain consequently makes it possible for us to have the facility for grasping what appear to be universals. So-called universals may be nothing more than generalizations of concrete experience or linguistic constructs of the mind.

I would add that the word "soul" in Aristotle's writings (upon which Thomistic hylomorphic thought is built) is amenable to a physicalist interpretation.

[END OF DIALOGUE]

Addendum: I want to make it clear that my comments pertain to human intellection, not divine (God or angels). It is my belief that human intellection only exists because of brain activity--not due to some immaterial intellect. We may not understand how the brain produces intellection, but evidence continues to lean in that direction.

I also have no problem using the term "mind." Mind would not exist if there were not physical (neurobiological) processes that obtained.