It was about the early part of the year 1652 that the calamity was
consummated. At the age of forty-three he was in total darkness.
The deprivation of sight, one of the severest afflictions of which
humanity is capable, falls more heavily on the man whose occupation
lies among books, than upon others. He who has most to lose, loses
most. To most persons books are but an amusement, an interlude between
the hours of serious occupation. The scholar is he who has found the
key to knowledge, and knows his way about in the world of printed
books. To find this key, to learn the map of this country, requires a
long apprenticeship. This is a point few men can hope to reach much
before the age of forty. Milton had attained it only to find fruition
snatched from him. He had barely time to spell one line in the book of
wisdom, before, like the wizard's volume in romance, it was hopelessly
closed against him for ever. Any human being is shut out by loss
of sight from accustomed pleasures, the scholar is shut out from
knowledge. Shut out at forty-three, when his great work was not even
begun! He consoles himself with the fancy that in his pamphlet, the
_Defensio_, he had done a great work (_quanta maxima quivi_) for
his country. This poor delusion helped him doubtless to support his
calamity. He could not foresee that, in less than ten years, the great
work would he totally annihilated, his pamphlet would he merged in the
obsolete mass of civil war tracts, and the _Defensio_, on which he had
expended his last year of eyesight, only mentioned because it had been
written by the author of _Paradise Lost_.

The nature of Milton's disease is not ascertainable from the account
he has given of it. In the well-known passage of _Paradise Lost_,
iii. 25, he hesitates between amaurosis (drop serene) and cataract
(suffusion)