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.