In the same letter Diderot avows his dissent--hypocritically, we find reason for suspecting--from Saunderson's conclusion. "It is commonly in the night-time," he says, "that the mists arise which obscure in me the existence of God; the rising of the sun never fails to scatter them. But then the darkness is ever-enduring for the blind, and the sun only rises for those who see." Diderot's denial of atheism seems more than suspicious, when one finds him taking so much pains to make out Saunderson's case for him, when he urges the argument following, for instance: "If there had never existed any but material beings, there would never have been spiritual beings; for then the spiritual beings would either have given themselves existence, or else would have received it from the material beings. But if there had never existed any but spiritual beings, you will see that there would never have been material beings. Right philosophy only allows me to suppose in things what I can distinctly perceive in them. Now I perceive no other faculties distinctly in the mind except those of willing and thinking, and I no more conceive that thought and will can act on material beings or on nothing, than I can conceive material beings or nothing acting on spiritual beings." And he winds up his letter thus: "It is very important not to take hemlock for parsley; but not important at all to believe or to disbelieve in God. The world, said Montaigne, is a tennis-ball that he has given to philosophers to toss hither and thither; and I would say nearly as much of the Deity himself."[75] In concluding our account of this piece, we may mention that Diderot threw out a hint, which is a good illustration of the alert and practically helpful way in which his mind was always seeking new ideas. We have common signs, he said, appealing to the eye, namely, written characters, and others appealing to the ear, namely, articulate sounds; we have none appealing to touch. "For want of such a language, communication is entirely broken between us and those who are born deaf, dumb, and blind. They grow, but they remain in a state of imbecility. Perhaps they would acquire ideas, if we made ourselves understood by them from childhood in a fixed, determinate, constant, and uniform manner; in short, if we traced on their hand the same characters that we trace upon paper, and invariably attached the same significance to them."[76] The patient benevolence and ingenuity of Dr. Howe of Boston has realised in our own day the value of Diderot's suggestion.