That oon of hem was blynd and myghte nat see,
But it were with thilke eyen of his mynde
With whiche men seen, after that they ben blynde.
– Geoffrey Chaucer
The Canterbury Tales, The Man of Law’s Tale. Constance and Hermengild meet a blind Christian man while they are out walking one day. The man could not see, says the Man of Law, unless it was with the eyes of the mind with which men see after they have become blind.