Ayn Rand -- Introduction to Objectivist Epistemology (1979, page 63)
But how is all of this done in a strictly material way?
I sometimes wonder whether she read Aristotle at all. Rand has the same problem that all empiricists do: bridging the gap between the knower and the thing known.
This other theory (ala John Locke) is often called "indirect realism" because it claims that we do not have direct access to extra-mental reality, but only indirect access, through impressions and ideas. Thus, on the Lockean view, there is a chain of causality: things affect us and our senses producing sense impressions and ideas, and these produce knowledge.There is, then, the obvious problem of knowing that our impressions are true representations of reality. There is no way to check them that does not itself rely on sensation and so is open to the same possibility of error. And since, on this view, one cannot tell if one's senses are delivering accurate information, one has reason to doubt that there is any referent for what one senses. One can reasonably (?) say that there is no extramental object (solipsism), or that there may or may not be an object, and we may or may not observe it accurately (relativism). The Thomistic theory cuts off bad consequences like these before they begin by denying that what we directly (and properly) perceive or know are sense impressions or our own ideas. Instead, what we perceive is the thing, and the sensible species (in the sense organ) is that by which the identity that is perception comes about. It works in an analogous manner for the intellect: what we know is the universal existing in the thing; the idea is that by which we know the universal.
Revealing ... your total ignorance regarding Ayn Rand.
"If there is a philosophical Atlas who carries the whole of Western civilization on his shoulders, it is Aristotle. He has been opposed, misinterpreted, misrepresented, and -- like an axiom -- used by his enemies in the very act of denying him. Whatever intellectual progress men have achieved rests on his achievements." -- Ayn Rand
And ... implying that Ayn Rand was an empiricist is akin to classifying the Pope as an atheist.