It is easy to see that this faculty which Blake calls "Imagination"
entails of itself naturally and inevitably the Christian doctrine of
self-sacrifice. It is in _Milton_ that Blake most fully develops his
great dogma of the eternity of sacrifice. "One must die for another
through all eternity"; only thus can the bonds of "selfhood" be broken.
Milton, just before his renunciation, cries--

I will go down to self-annihilation and eternal death
Lest the Last Judgment come and find me unannihilate,
And I be seiz'd and giv'n into the hands of my own Selfhood.

For, according to Blake, personal love or selfishness is the one sin
which defies redemption. This whole passage in _Milton_ (Book i., pp.
12, 13) well repays study, for one feels it to be alive with meaning,
holding symbol within symbol. Blake's symbolism, and his fourfold view
of nature and of man, is a fascinating if sometimes a despairing study.
Blake has explained very carefully the way in which the visionary
faculty worked in him:--

What to others a trifle appears
Fills me full of smiles or tears;
For double the vision my Eyes do see,
And a double vision is always with me.
With my inward Eye, 'tis an old Man grey,
With my outward, a Thistle across my way.

* * * * *

Now I a fourfold vision see,
And a fourfold vision is given to me;