Wall upon wall, the gross flesh hems it in,
This perfect, clear perception—which is truth.
A baffling and perverting carnal mesh
Binds it, and makes all error: and, to know,
Rather consists in opening out a way
Whence the imprisoned splendor may escape,
Than in effecting entry for a light
Supposed to be without. Watch narrowly
The demonstration of a truth, its birth,
And you trace back the effluence to its spring