The Logical And Phenomenological Possibility Of Hallucinations

The very possibility of hallucinations is rooted (besides in that it is consistent with logical axioms) in the fact that consciousness is not the same as the external world it can perceive, even if the world of matter and the perceptions of that matter aligned perfectly--not that one could know this was the case.  To perceive matter differently than it is, one must have experiences that are separate from the material plane, and thus, hallucinations by necessity occur in an immaterial way.  One can certainly know with absolute certainty that consciousness is immaterial aside from this particular issue by realizing that it is logically possible for a mind to exist without a body--there is no contradiction of axioms or any necessary truth in this, as there would be in a mind both existing and not existing at one--and that the concept of a body and mind are distinct.

They could also discover that a body without a mind is inanimate, so clearly a mere physical mass is not the same as a conscious being that happens to have a material form in which its mind resides.  As I like to point out, there would be no ultimate difference between a corpse and a live person besides the presence of consciousness.  Indeed, the physical differences between a live and dead body, such as the beating of the heart and the activity of neurons, are observed to accompany seeming consciousness, not that scientific correlations are at the same level as logical necessities.  The major difference, though, is consciousness or its absence.  This is the only utterly foundational metaphysical distinction between the two.

There still are or could be correlations, seeming causal relationships, between certain physical events in the nervous system and states of consciousness.  Whether these are actual causal connections or just perception-based correlations is of course unknowable for humans, but it does not contradict any of these other logical truths.  It could not.  Contradicting logical axioms and what follows from them or from some other necessary truths is all that makes something impossible in that it could not and never could have been the case, and even an idea as familiar to many as hallucinations being logically and phenomenologically possible actually relies on the mind's immateriality.  No hallucinations could have ever been experienced (people just could not know this), and it would still have to be true that hallucinations are logically possible, and this alone requires that consciousness is not physical.

It is true that at least some hallucinations could be triggered on a phenomenological level by the activity of neurochemicals, and it is still true that, though this is true independent of this for the aforementioned reasons and thus knowable apart from this, the potential to perceive objects, people, or environments that are not actually there beyond one's mind necessitates that the mind and matter are not identical.  If the latter is natural as matter must be, then the former must be immaterial.  The exact causal origin or background correlation in the extended nervous system is irrelevant to this.  Consciousness and all of the imagery, sensory perceptions (which are not the same as external stimuli), emotions, and desires therein could only be nonphysical, just as matter can only be physical.