Since knowledge is but sorrow's spy,
'Tis better not to know."
But the source of Gray's apothegm is still more obviously traceable to these lines in Prior:
"Seeing aright we see our woes;
Then what avails us to have eyes?
From ignorance our comfort flows,
The only wretched are the wise."
A third sample in Gray is borrowed from Milton. The latter, in speaking of the Deity, has this beautiful image:
"Dark with excessive light thy skirts appear."
And Gray, with true poetic feeling, has applied this image to Milton himself in those forceful lines in the Progress of Poesy, in which he alludes to the poet's blindness: