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.