Man is a natural entity among natural entities. All human knowledge comes to humans via the senses (images, etc.). Insofar as matter as such is unintelligible to us, and pure essences are inscrutable to us, we must somehow "bridge" our sensory contact with the world and our intellectual descriptions of it. We do this by "abstracting" a thing's nature from our sensory contact with it. We know universals IN particulars, not AS particulars; and we know particulars BY universals, not AS universals.
The problem is this: just because we cannot think without "images" does not mean we think only BY images. The problem is this: can we STOP at our private visualizations (as an adequate grasp of reality)? Thomism insists all thought involves a visual dimension but abstraction is a purely intellectual act, and therefore surpasses total visualization. Just because we can't speak without word doesn't mean we can say all we know IN words. We don't "know" essences themselves; we know things IN their act of existence; and the plenitude of existence endlessly surpasses our verbal or visual description of it.
It's not an "empirical verifiable" fact that "knowledge is a function of empirical verification." What's more, that claim ITSELF cannot be verified empirically. It begs the question. Being a claim ABOUT empirical facts, empirical verificationism is not itself an empirical FACT.
Kant reminds us of the crucial "unity of consciousness," but is such a thing empirically measurable? And what about "now" itself? Can we "touch" or "measure" the present? The present has no extension or duration since it either "just was" or "is about to be" but it exists in a transcendental way. It is the transcendental "dimension" which enables us to have empirical experience at all.
Tell me what is happening RIGHT NOW. You can't, because "now" is already "past." The "now" obviously it exists, but it is not subject to an empirical description at all, nor a direct empirical verification. Can we measure the present? WHEN we do measure it? We only "measure" the duration of "now" on the boundaries of it. It's like trying to look at the inside of your own eyeball.