But Bryan Magee's remarkable new book on the subject is not concerned with the rights and wrongs of how blind people are stigmatised and alienated. A senior philosopher, he became interested in blindness as part of a theoretical debate about a classical dilemma: do we achieve knowledge of the world through experience (as empirical philosophers would have it), or is it the product of intellectual learning and contemplation - the Platonic idea? He suggests that all of us are handicapped by the limitations of our own sensory equipment (we do not see as avidly as hawks, say); but we are not, he is sure, as handicapped as blind people. Do they, he wonders, apprehend an entirely different world? If so, what does this tell us about the nature of knowledge? To find out, he opened a correspondence with Martin Milligan, the blind head of philosophy at Leeds University. The letters are published here, in a form necessarily truncated by Milligan's death. But what survives is a superb document - a lively and acute philosophical dialogue pitched at a high level of intellectual seriousness, written in the readable style of a letter to a pal, and kindled by the full range of human reflexes - zeal, curiosity, defensiveness, touchy pride.
Milligan, the hero of the book, begins by rewriting the question Magee has asked him, Magee asks: "How do I know that I am blind?" and Milligan gives it a twist: "Why do I think it reasonable to believe that I am blind?" Immediately, the focus of the argument sharpens. Milligan, it is clear, is not willing to accept Magee's confident terms. He does not "know", through experience, that he is blind, because he has no experience of light with which to compare it. He simply has to take other people's word for it. This is not, though, merely a way of giving priority to intellectual knowledge over knowledge felt along the pulse. Blindness, it emerges, is itself an experience, and one that does seem to call forth an enhancement in the other senses. Milligan writes beautifully about the way blind people sense objects as "air-thickening occupants of space" - and know acoustically the difference between a hedge and a wall.
It is not possible, in precis, to do anything like justice to the metaphysical details of the conversation. It ranges over the meaning of a lake full of flamingoes, the taste of coffee, the facial expressions of George Bush, the difference between a picture and a map (Milligan, tellingly, argues that a map is more expressive).Many of the best moments flow from the tetchy relationship between the two men. Magee is determined that Milligan should admit the extent of the loss felt by blind people. Milligan politely refuses. At one point Milligan chides his co-author for his assumption that blind people inhabit a diminished world; Magee retorts that he made no such assertion, and boasts about his credentials as a liberal thinker. Milligan apologises with delicious coolness: "I did not know the full extent of your splendid work in the humanist cause in the `sixties'." You sense a big philosophical statement coming up, about the relationship between inverted commas and life, but, alas, it never comes.
It is a shame in a way that Magee has the last word, and uses it to refute most of what Milligan has said. He seems to think it axiomatic that readers will have found Milligan's arguments self-serving and narrow. When Milligan disputes his premises, Magee accuses him of getting "sidetracked". Perhaps, he muses, Milligan was terrified to admit how much pleasure he was missing out on. Readers might see Milligan's equanimity as the higher and subtler achievement. The way things look, he insists, is not an accurate guide to the way things are. Who could disagree?