Dissociative Identity Disorder

The state of someone having multiple personalities, a condition once called multiple personality disorder but now commonly referred to as dissociative identity disorder, is only possible because of metaphysical truths that are neglected, misunderstood, or taken for granted by many even outside the context of dissociation.  The dissociative phenomenon of experiencing disconnected thoughts or erratic concentration, something even people without the disorder might relate to, is taken to its greatest extreme in those who literally develop more than a single personality, with each potentially having its own memories, whether genuine or false (not that anyone can logically prove their memories of events are accurate anyway), along with preferences and worldviews.  The explicitly philosophical ramifications are there for anyone who has thought of extreme dissociation to realize.

In those with dissociative identity disorder, the same body is inhabited by multiple personalities that can be so distinct that, if more than one mind is not actually present in the body, it is as if there are truly multiple consciousnesses all dwelling in the same physical shell.  Consciousness is nonphysical and thus does not occupy metaphysical space in the same way that even the smallest material object does, so there is nothing logically impossible about the concept of multiple personalities of the same person or even more than one truly separate mind inhabiting a single body--however, it would not logically follow from this or from the basic idea of dissociative identity disorder that any of the minds would know of each other's presence.  Logical possibility is metaphysical possibility and yet this does not allow one to know anything more than that something is not impossible.

Not only could one never know if they have other personalities they cannot perceive precisely because they cannot perceive it--the existence, contents, and immediate sensory or memory perceptions of one's consciousness are absolute certainties, and some of the only ones that can be discovered, yet a totally dissociative state of mind would be inaccessible to the standard conscious experience of a person's mind.  Although such a level of dissociation is logically possible and metaphysically significant because it entails multiple fragmented, distinct parts of a mind or almost multiple minds residing in a shared body, it cannot be known to be occurring or not occurring.  What can be known about the subject is just what dissociation is, which types are logically possible, the epistemology of introspection, and the metaphysics of general consciousness.

The metaphysics of dissociative identity disorder, like all things, is rooted in and revealed by reason, and one of the things reason reveals is that conscious experience cannot be used to perceive things that are unperceived, with dissociative states being separate from ordinary introspective experience by default.  One can experience conflicting or even unexpected sides of one's consciousness coexisting alongside each other; this much can be experienced by anyone with even rudimentary levels of nuance to their personality.  However, like how one could never know if the only logically possible version of the subconscious (with the subconscious being a somewhat unified background or extension of the conscious part of one's metaphysical mind), one would need to be free of human epistemological limitations to know if one is not psychologically fragmented in this way--or somehow literally sharing a body with an undetected second consciousness.