LITMIR.BIZ

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by Rousseau, when all three were needy wanderers about the streets of Paris. They used to dine together once a week at a tavern, and it was Diderot who persuaded a bookseller to give Condillac a hundred crowns for his first manuscript. "The Paris booksellers," says Rousseau, "are very arrogant and harsh to beginners; and metaphysics, then extremely little in fashion, did not offer a very particularly attractive subject."[65] The constant intercourse between Diderot and Condillac in the interval between the two works of the great apostle of Sensationalism, may well account for the remarkable development in doctrine. This is one of the many examples of the share of Diderot's energetic and stimulating intelligence, in directing and nourishing the movement of the time, its errors and precipitancies included. On the other hand, the share of Condillac in providing a text for Diderot's first considerable performance, is equally evident.

      The Letter on the Blind is an inquiry how far a modification of the five senses, such as the congenital absence of one of them, would involve a corresponding modification of the ordinary notions acquired by men who are normally endowed in their capacity for sensation. It considers the Intellect in a case where it is deprived of one of the senses. The writer opens with an account of a visit made by himself and some friends to a man born blind at Puisaux, a place seventy miles from Paris. They asked him in what way he thought of the eyes. "They are an organ on which the air produces the same effect as my stick upon my hand." A mirror he described "as a machine which sets things in relief away from themselves, if they are properly placed in relation to it." This conception had formed itself in his mind in the following way. The blind man only knows objects by touch. He is aware, on the testimony of others, that we know objects by sight as he knows them by touch; he can form no other notion. He is aware, again, that a man cannot see his own face, though he can touch it. Sight, then, he concludes, is a sort of touch, which only extends to objects different from our own visage, and remote from us. Now touch only conveys to him the idea of relief. A mirror, therefore, must be a machine which sets us in relief out of ourselves. How many philosophers, cries Diderot, have employed less subtlety to reach notions just as untrue?

      The born-blind had a memory for sound in a surprising degree, and countenances do not present more diversity to us than he observed in voices. The voice has for such persons an infinite number of delicate shades that escape us, because we have not the same reason for attention that the blind have. The help that our senses lend to one another, is an obstacle to their perfection.

      The blind man said he should have been tempted to regard persons endowed with sight as superior intelligences, if he had not found out a hundred times how inferior we are in other respects. How do we know—Diderot reflects upon this—that all the animals do not reason in the same way, and look upon themselves as our equals or superiors, notwithstanding our more complex and efficient intelligence? They may accord to us a reason with which we should still have much need of their instinct while they claim to be endowed with an instinct which enables them to do very well without our reason.

      When asked whether he should be glad to have sight, the born-blind replied that, apart from curiosity, he would be just as well pleased to have long arms: his hands would tell him what is going on in the moon, better than our eyes or telescopes; and the eyes cease to see earlier than the hands lose the sense of touch. It would therefore be just as good to perfect in him the organ that he had, as to confer upon him another which he had not. This is untrue. No conceivable perfection of touch would reveal phenomena of light, and the longest arms must leave those phenomena undisclosed.

      After recounting various other peculiarities of thought, Diderot notices that the blind man attaches slight importance to the sense of shame. He would hardly understand the utility of clothes, for instance, except as a protection against cold. He frankly told his philosophising visitors that he could not see why one part of the body should be covered rather than another. "I have never doubted," says Diderot, "that the state of our organs and senses has much influence both on our metaphysics and our morality." This, I may observe, does not in the least show that in a society of human beings, not blind, but endowed with vision, the sense of physical shame is a mere prejudice of which philosophy will rid us. The fact that a blind man discerns no ill in nakedness, has no bearing on the value or naturalness of shame among people with eyes. And moreover, the fact that delicacy or shame is not a universal human impulse, but is established, and its scope defined, by a varying etiquette, does not in the least affect the utility or wisdom of such an artificial establishment and definition. The grounds of delicacy, though connected with the senses, are fixed by considerations that spring from the social reason. It seems to be true, as Diderot says, that the born-blind are at first without physical delicacy; because delicacy has its root in the consciousness that we are observed, while the born-blind are not conscious that they are observed. It is found that one of the most important parts of their education is to impress this knowledge upon them.[66]

      But the artificiality of a moral acquisition is obviously no test of its worth, nor of the reasons for preserving it. Diderot exclaims, "Ah, madam, how different is the morality of a blind man from ours; and how the morality of the deaf would differ from that of the blind; and if a being should have a sense more than we have, how wofully imperfect would he find our morality!" This is plainly a crude and erroneous way of illustrating the important truth of the strict relativity of ethical standards and maxims. Diderot speaks as if they were relative simply and solely to our five wits, and would vary with them only. Everybody now has learnt that morality depends not merely on the five wits, but on the mental constitution within, and on the social conditions without. It is to these rather than to the number of our senses, that moral ideas are relative.

      Passing over various other remarks, we come to those pages in the Letter which apply the principle of relativity to the master-conception of God. Diderot's argument on this point naturally drew keener attention than the more disinterestedly scientific parts of his contribution. People were not strongly agitated by the question whether a blind man who had learned to distinguish a sphere from a cube by touch, would instantly identify each of them if he received sight.[67]

      The question whether a blind man has as good reasons for believing in the existence of a God as a man with sight can find, was of more vivid interest. As a matter of fact, Diderot's treatment of the narrower question (pp. 324, etc.) is more closely coherent than his treatment of the wider one, for the simple reason that the special limitation of experience in the born-blind cannot fairly be made to yield any decisive evidence on the great, the insoluble enigma.

      Here, as in the other part of his essay, Diderot followed the method of interrogating the blind themselves. In this instance, he turned to the most extraordinary example in history, of intellectual mastery and scientific penetration in one who practically belonged to the class of the born-blind; and this too in dealing with subjects where sight might be thought most indispensable. From 1711 to 1739 one of the professors of mathematics at Cambridge was Nicholas Saunderson, who had lost his sight before he was twelve months old. He was a man of striking mental vigour, an original and efficient teacher, and the author of a book upon algebra which was considered meritorious in its day. His knowledge of optics was highly remarkable. He had distinct ideas of perspective, of the projections of the sphere, and of the forms assumed by plane or solid figures in certain positions. For performing computations he devised a machine of great ingenuity, which also served the purpose, with certain modifications, of representing geometrical diagrams. In religion he was a sceptic or something more, and in his last hours Diderot supposes him to have engaged in a discussion with a minister of religion, upon the arguments for the existence of a deity drawn from final causes. This discussion Diderot professes to reproduce, and he makes Saunderson discourse with much eloquence and some pathos.

      By one of those mystifications which make the French polemical literature of the eighteenth century the despair of bibliographers, Diderot cites as his authority a Life of Saunderson, by Dr. Inchlif. He sets forth the title with great circumstantiality, but no such book exists or ever did exist. The Royal Society of London, however, took the jest of fathering atheism on one of its members in bad part, and Diderot was systematically excluded from the honour of admission to that learned body, as he was excluded all his life from the French Academy.

      The reasoning which Diderot puts into the professor's mouth is at first a fervid enlargement of the text, that the argument drawn from the wonders of nature is very weak evidence

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