The prophet Ezekiel reported (in 4:4-8) that God told him to lay on his right side for three months, then on his left side for three months, as a warning to the Hebrews. In a vision Blake asked him why he did it and got this reply: "the desire of raising other men into a perception of the infinite" (Blake reported this to us in MHH Plate 13 (line 21ff).
"The desire of raising other men into a perception of the infinite": by and large that was Blake's main purpose in his creative endeavors.
There are many kinds of seeing and many levels of consciousness, but, resorting to the natural proclivity for the dialectic, we might say there are two:
1. The sense-based, natural, materialistic time and space consciousness, with no spiritual awareness. Blake called this Ulro; Jesus called it Hell.
2. Vision, coming forth from the inner man, the Light, the Now. It's a different kind of consciousness, a perception of the infinite (Blake called it Eden; Jesus called it the Kingdom of Heaven or the Kingdom of God).
Jesus showed us with his life how to live eternally; and he told us we could do it. Blake did it, periodically at least, and like Jesus he wanted us to share that heavenly gift.
He called it Vision; that's what he lived for; those eternal moments when he perceived the infinite were all that mattered. If you can't do it continuously, then you can talk about it, write about it, draw it, paint it. He did (and you can) show us how to see.
(This material was largely taken from the Blake Primer, near the beginning.)
Re double vision: "This is a cogent description of what he calls double vision, an attribute of schizophrenics as well as artists; they see what's not there to the sense based person." (Double vision appears to be closely related to intuition.)
Look also at twofold.
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