Leslie Brisman sees lines 336-42 "as approaching the apex of the sublime, the point where the history of the past breaks off into apostrophe and eternal presence" (120). Here are the lines:
When light is changed to love, this glorious One
Floated into the cavern where I lay,
And called my Spirit, and the dreaming clay
Was lifted by the thing that dreamed below
As smoke by fire, and in her beauty's glow
I stood, and felt the dawn of my long night
Was penetrating me with living light.
Brisman writes:
The cavern image, important to the prophetic analogue for such experience, recalls "the caverns of my dreamy youth" and makes of life generally, as Plato did in the famous myth, a cave but occasionally visited by light. Almost magically, the passage manages to retain its reservations about the externality of transcendental experience in the very phrases that describe it. The illumination is not from above but from below--internal, as it were--and "the dawn of my long night" is a dawn as much the property of as an interference upon the night of life. The passage ostensibly records that which surpasses and redeems one from dream; but dreamy clay is lifted by "the thing that dreamed below," and dream vision remains the source of transcendence. (120)
Brisman, Leslie. "Epipsychidion." Modern Critical Views: Percy Bysshe Shelley. Ed. Harold Bloom. New York: Chelsea House, 1985. 113-120.