among the most consistently reported experiences in high-dose psychedelic states is ego dissolution: the temporary disappearance of the sense of being a separate self. Not the loss of consciousness, the person is typically quite alert and capable of experience. The loss, specifically, is of the boundary between self and world, between subject and object, between "me" and "everything else."
This sounds alarming, and in poorly supported settings, it can be. But in appropriate contexts, a large proportion of people who have this experience describe it as among the most meaningful of their lives. The psychologist William James, appearing again, because he was ahead of his time in almost everything, described a very similar state induced by nitrous oxide and proposed that it was noetic: it felt not merely emotional but like a genuine disclosure of something about the nature of reality.
Philosophically, ego dissolution is interesting precisely because it is so philosophically unexpected. Most of us operate on the background assumption that the self is a given, a starting point, the one thing we cannot doubt (Descartes' cogito is the extreme version of this). But ego dissolution suggests that the felt sense of being a separate self is a construction, a product of ongoing neural processes that can be temporarily suspended, rather than a metaphysical bedrock.
The Buddhist philosophical tradition has been saying exactly this for 2,500 years. The doctrine of anatta (non-self) in Buddhism holds that what we ordinarily experience as a persistent, unified self is actually a constantly changing bundle of processes, thoughts, sensations, perceptions, intentions, with no fixed owner or center. The sense of being a self is a useful fiction, not a metaphysical fact. Remarkably, many people who have psychedelic ego dissolution experiences independently report something that sounds very close to this: not the destruction of experience but the revelation that experience has no fixed experiencer.
Thomas Metzinger, in Being No One (2003) and The Ego Tunnel (2009), has developed a rigorous philosophical account of this that is broadly consistent with both the Buddhist analysis and the psychedelic phenomenology. Metzinger's claim: the self is a phenomenal self-model, the brain's representation of itself as an entity, not a metaphysical substance. Ego dissolution is what happens when this model is temporarily destabilized. The resulting experience feels like profound contact with reality precisely because the self-model, in normal life, is a thin, persistent filter between experience and what might be called "pure experience", experience without an experiencer.
The philosophical payoff: if Metzinger is right, and if psychedelic states partially validate the Buddhist analysis, then the default Western philosophical assumption that the self is the unquestioned starting point of inquiry is exactly backwards. The self is the thing to be explained and examined, not the thing that does the explaining and examining from a safe vantage point above the action.