Many years ago, as I was leafing through a book in which I had no interest, I found one of the saddest stories in the world. It was a new edition of a textbook on visual perception, the psychology and physiology of the eye, and there I discovered “the case of S.B.” S.B. was an Englishman who was blind from infancy to middle age, when, at the age of 52, he received a successful corneal transplant. “All his life he tried to picture the world of sight,” Richard L. Gregory wrote. “He longed for the day when he might see. ... But though the operation was a success his story ended tragically.” With his sight recovered, S. B. managed to identify animals and objects correctly on the basis of the prior knowledge that he had gained from touch and the reports of sighted people, “but he found the world drab, and was upset by flaking paint and blemishes.” I will let Gregory complete the tale: “[He] said that he noted more and more the imperfections in things, and would examine small irregularities and marks in paintwork or wood, which he found upsetting, evidently expecting a more perfect world. He liked bright colours, but became depressed when the light faded. His depression became marked and general. He gradually gave up active living, and three years later he died.”

I never forgot S.B., the man whose heart was broken by the ugliness of the world. In my unceasing and unsuccessful attempt to work out the relations between idealism and realism, he exemplified most purely the disappointed idealist, and also the chronic connection between idealism and blindness. How much can an idealist know about the world and still not be defeated by it? Consider love: blind love is surely an inferior sort of love—the expression of the fear that the object of love may not be sufficient to justify it; but hope, too, must face the problem of ignorance. With too little knowledge, hope may be a delusion; with too much knowledge, hope may be destroyed. To some extent, idealism is always a defiance of the facts—but defy too many of the facts and you court disaster. People who wish to change the world have a special responsibility to acquaint themselves with the world, in the manner of scouts or spies. The realist, by contrast, has no conscience about being complicit with the world. For the realist, the world is all there is to work with. He sees no virtue and no glamour in adopting a standpoint outside reality: it would only diminish his efficacy, which is his highest wish. He does not promote his goals into ideals. Aspiring to less, the realist may accomplish more. Aspiring to more, the idealist may accomplish less.

And yet even the failed idealist adds to the store of the world’s sense of possibility. Idealism is futural: it is never completely defeated because it is never completely satisfied. The aspirations of the realist nourish only his own time: they are premised on the actualities of the present, and so they bequeath nothing to those who will live in a different present with different actualities. But idealism is an activity of the imagination, which is less than vision but more than blindness. It is visionary, in that it beholds what is not yet there. The facts surpass only the poor imaginations. The world may thwart our efforts to improve it, but it cannot thwart our conceptions of it improved; and that is our advantage over it. We can always resume the struggle.

S.B.’s mistake was in not regarding the ideal temporally. He believed that the world was already perfect. What he could not see must therefore have been perfect: perhaps this was his private theodicy, his way of conferring significance upon his blindness. He might have found more comfort in the thought that the world was not worth seeing; but he aspired to sight. How can the blind not believe in beauty? I thought of S.B. last week as I stood before The Great Piece of Turf, Dürer’s heart-stopping watercolor of 1503, in the National Gallery. It depicts only a homely clump of grass, with plantain and dandelion, in a muddy patch of dirt. This picture is a miracle not only of the artist’s hands, but also of the artist’s eyes. When Dürer saw those weeds, he saw the occasion for an apotheosis of naturalism in Western art. In the marginal he perceived the monumental. But S.B.—would he have seen only more drabness, more irregularities, more blemishes? And not only S.B.: it is fine for us to marvel at the picture, but would we have marveled also at what it shows? We, who are always still learning to see, would not even have noticed it. It was dull, after all, until Dürer demonstrated that it was exciting.

The Great Piece of Turf is a masterpiece of the morality of noticing, a genuinely thrilling example of the redemption of the unperceived world by perception. Realism in art is not like realism elsewhere. In art, realism, too, is an accomplishment of the imagination. What is imagined is the world as it really is; or the world as it would appear if it were totally visible, or if we were totally able to see it. (I first grasped this on a delirious autumn day in Bruges, where I stood for hours contemplating the detail in van Eyck’s The Madonna with Canon van der Paele.) Dürer’s picture, with its meta-empirical precision, was produced not in the mud but in his studio, and shows a low-to-the-ground perspective that could not have been his own—“a worm’s-eye view of heterogeneous nature,” as Joseph Koerner calls it. So the painter’s eyes were only the beginning. The verisimilitude with which he rendered the dense scene—the almost microscopic clarity of the soaring or languid blades of grass in this humble thicket—was not the mere record of a man’s optical observations. The uncanny likeness is a fantasy of the actual. As such, it is a lesson in looking; and also in the collapse of the dichotomy between the ideal and the real. They are barren without each other. Realists can also be blind and idealists can also see. I left the gallery dreaming of recovered sight.