The reason for the continued confusion on this issue is that all three
alternatives are frankly incredible!
Direct Perception is incredible because it suggests that we can have
experience out beyond the sensory surface, in violation of everything
we know about the causal chain of vision.
Visual illusions are an embarrassment for Direct Perception because
the illusory edges and surfaces appear out in the world on the page
where the stimulus is printed, although they are obviously the result
of processing in the brain.
The phenomena of dreams and hallucinations are also problematic for
Direct Perception because they demonstrate the capacity of the brain
to construct complete virtual worlds, a capacity which must surely be
employed also in normal spatial perception.
Finally, Direct Perception offers no clue as to how an artificial
vision system could possibly be endowed with the kind of external
perception that we observe in visual consciousness.
The theory of Direct Perception is as mysterious as the property of
consciousness which it attempts to explain!
Indirect Perception is also incredible, for it suggests that the world
that we see around us is actually inside our head. This can only mean
that the head which we have come to know as our own, is not our true
physical head, but merely a miniature perceptual copy of our head
inside a perceptual replica of the world, all of which is contained
within our physical head.
Stated from the internal phenomenal perspective, beyond the farthest
things that we can perceive in all directions, i.e. beyond the walls,
floor, and ceiling of the room you see around you, is the inner
surface of your true physical skull. And beyond that skull is an
unimaginably immense external world of which all this that you see
around you here is merely an internal virtual-reality replica.
The existential vertigo occasioned by this mental image is so
disorienting that only a handful of researchers have seriously
entertained this notion, or taken it to its logical conclusions.
Indirect Perception suggests a three-dimensional volumetric imaging
mechanism in the brain for which no direct neurophysiological evidence
has been found.
Projection Theory is also incredible because no medium or carrier has
ever been discovered projecting information outward from the
brain. The flow of visual information is exclusively uni-directional:
from the world, through the eye, to the brain. The external world and
its perceptual replica cannot be spatially superimposed, because one
is inside your head and the other is outside.
The pheomena of dreams and hallucinations are also problematic for a
Projection Theory for they produce an experience much like normal
perception, and yet for some reason they are not projected but
remain internal to the brain.
Finally, Projection Theory offers no clue as to how an artificial
vision system could be constructed to project as in our own
The Projection Theory is also as mysterious as the property of
consciousness which it attempts to explain.