What is the meaning of the quote from Edgar Allan Poe's "The Pit and the Pendulum" listed below?"But if the impressions ... are not, at will,...

But if the
impressions of what I have termed the first stage, are not, at will, recalled,
yet, after long interval, do they not come unbidden while we marvel whence they
come?

This quote
is spoken by the narrator in the beginning paragraphs of Poe's Gothic horror "The Pit
and Pendulum." The narrator explains he had just swooned. He has commenced to tell his
epiphanies about the state of consciousness resulting from (or confirmed by) his
swoon.

He explains that when returning to consciousness
from a swoon--a state, he claims, in which some small shred of conscious awareness still
remains--there are two stages to go through. The first stage is that in which mental or
spiritual awareness returns: you regain awareness of your perceptual capacities,
thoughts, impressions, humanity, etc. The second stage is that in which physical
awareness returns: you regain awareness of your bodily existence and physical parts and
capabilities.

The narrator suggests that in the first stage
of recovery to consciousness from a swoon impressions are retained of what exists on the
far side of conscious experience, in what he calls "the gulf beyond" consciousness, the
gulf that is unconsciousness, as one might retain the memory of a dream while rousing
from sleep. Impressions of the gulf can exist, as he asserts, because some small bit
consciousness awareness always remains, "even in the
grave."

He suggests that in the second stage of recovery to
consciousness it might be possible to access the impressions held in the first stage,
just as one fully awakened can sometimes recall the dreams of sleep. Then he suggests
that if these impressions fade away in the second stage with the coming of physical
awareness, as dreams fade away, they might return to conscious thought at some time in
the future and that if they were to do so, one wouldn't know their origin: one wouldn't
have a way to associate the rising impression about the gulf of unconsciousness with
one's previous swoon. Therefore, one would be puzzled as to the origins and meaning of
these seemingly random and inexplicable
thoughts.

Quote:
"But if the impressions ... are not, at will, recalled, yet, after long interval, do
they not come unbidden, while we marvel whence they come?"

Paraphrase:
But if the impressions are not intentionally recalled but at some remote future time
voluntarily resurface to consciousness, aren't the impressions revived without being
called forth, and will we not wonder at where these thoughts have come
from?