There lived a race of men in a cavern deep in the earth who hunted the
blind fish swimming in subterrennean pools long severed from some
forgotten ocean.  They called themselves no name, for they had no
stories of the people of the world above to differentiate against.
The only light they knew, save for luminescent lichens, was a faint
pink-blue shimmer on the wall of the cavern from a crooked quartz
shaft which refracted the radiance of the sun and the moon.  The
lichens they could touch and know what it was that fell upon that dim
sense of sight, but the blur of light from the crystal unguessably
high above was the only facet of their chthonic existence that was
beyond understanding.  

The shifting of the earth surfaced a vein of quartz where the shimmer
struck the wall.  This caused a reflection to appear on the floor,
more blurred but otherwise resembling the swirl of colors on the wall.
For the first time, the people could touch light, but found it had no
weight or substance, save that catching it gave rise to a new thing:
shadow.

Their hitherto yieldless comprehension of the universe fell into
fragments, turbulence driving vortices of revelatory thoughts.
Madness took hold of a few in the newfound sensation of being
ungrounded, most especially those invested in perpetual stasis.

Slowly and silently, with neither desire nor active intent, a faction
grew amongst the people that became unassailable.  They were called, to
render crudely in our tongue, the Dream Walkers.  For so is it they
observed:  if the blur of light on the floor is but the imperfect
reflection of the light upon the wall, can it not be that the blur of
light on the wall is but a flawed representation of some purer source?
And of that source, can it not also be but a mirroring?  So on, ad
infinitum.

So they thought of dreams.  Since a dream is the substanceless reflection
of waking life, vanishing into nothingness upon the cessation of
sleep, how is it we casually suppose that being awake, for its gross
particularity, is not some figment in a greater Dream?