For nineteen years he had lived as one in a dream: he looked without seeing, listened without hearing, forgetting everything, almost everything. When he fell, he became unconscious; when he came to, the present was almost intolerable in its richness and sharpness, as were his most distant and trivial memories. Somewhat later he learned that he was paralyzed. The fact scarcely interested him. He reasoned (he felt) that his immobility was a minimum price to pay. Now his perception and his memory were infallible. (trans. James E. Irby)
To be able to see everything in its slightest detail and remember every detail: what an amazing ability and what a torture. For him, he could see aging occur by the second. His own hands one second are not the same in the next: he can perceive how they had changed in that second, and remember that change perfectly.
He was, let us not forget, almost incapable of ideas of a general, Platonic sort. Not only was it difficult fo rhim to comprehend that the generic symbol dog embraces so many unlike individuals of diverse size and form; it bothered him that the dog at three fourteen (seen from the side) should have the same name as the dog at three fifteen (seen from the front).
But, indeed, here is the rub. With perfect perception and perfect memory, how does one actually comprehend? How can one create thought? Does not thought involve generalization and categorization and so forth? Does it not involve organizing? In short, does not thought necessitate a certain degree of forgetting? Funes lives in a pure world of experience, of details. Yet he cannot see similarity, but only difference. He cannot compare, but only contrast. When everything, absolutely everthing, is different and must have its own label (even what we "vaguely" perceive as the same dog a minute later), how does one actually take in the world? When you see every detail, the smallest, minutiae, a single room may be overwhelming with pulsating life, much less anything larger.
With no effort he had learned English, French, Portuguese, and Latin. I suspect, however, that he was not very capable of thought. To think is to forget differences, generalize, make abstractions. In the teeming world of Funes, there were only details, almost immediate in their presence.
Interestingly, the narrator proceeds to tell the story in the manner of forgetting, that is, through indirect, and therefore imprecise, speech. One person's memory of another's perfect memory is itself imperfect, a product of forgetting, and therefore capable of secondary reflection, of thought.