Ego Death and the Collective Unconscious From my experience, an ego death is something that is temporary and is not a spiritual as some may claim it to be. It is definitely a real phenomenon, which can be induced by things such as meditation and psychedelic drug use.
To begin, I think it is important to realize the self is not a thing to be had and lost. It is not a substance of any kind, unless you subscribe to a form of dualism. It is rather an ability to integrate information and understand a vantage point in relation to stimuli. This seems very counter intuitive , I know, and it is very difficult to talk about self-hood without referring to it as something to that can be obtained. "the self" is a form of proprioception. It is a relationship between one organized system and another. When the ability to relate to information is lost, the whole feeling of having a place in which you are related to something is lost as well.
What we recognize as the single self that we are instead seems to be an aggregation of various view points, which often conflict with one another. This concept of an ego arises naturally with life, which a definition of will hardly ever go uncontested. Minimal life seems to be a system that undergoes self organization, has a semi-permeable membrane, and reacts with the environment in a way that allows for a transfer of matter. This last point is metabolism. A further point would include cognition, which under some understandings is merely efficiency with the environment. In other words, when one cognizes something, it requires an environment to provide inputs, and the living system provides outputs in the ways of behavior, and often merely thoughts in humans. I am not claiming to know how this mystery of life arises, only how we can potentially understand it compared to non-living things. With the arrival of these criteria, naturally comes a self or agency. Life is organization of matter, rather than matter itself. So, similar to the self or ego, it is a pattern, or relationship to the environment.
Now, consciousness of this phenomenon is a very complex, and scarcely understood, concept, which I may no claim to being able to explain. But, I subscribe to a form of identity theory and personally believe that it is identical with brain processes, but does not completely reduce to them. That is because consciousness is a perspective of these brain processes from a subjective vantage point, but does indeed exist and guide us. So, what I'm trying to say, is that even though consciousness and brain processes are the same thing, the way that consciousness is experienced sets it apart from the way that brain process are experienced; namely through the third-person perspective. I personally believe that the point of consciousness is to augment attention processing in order to enhance the ability to hold information in working memory and to focus on certain things more effectively, but this needs more scientific testing.
So, with this being said, the feeling of ego-death is the failure to recognize that one is an organized system that has separated itself from the normal organization of the environment and can. Life is a self-perpetuating system that moves through the environment, exchanging matter, but ultimately "following its own rules." So, when this recognition falls away, it is not very surprising that one feels as if they are one with everything else; I mean, technically we are. We're embedded in this universe, but our embodiment produces a feeling of separation, which is supported by our bodily organization, and made seeming obvious by our membrane, i.e. body boundary. When one realizes that they are one with everything, its just a transcendence beyond the organizational boundaries forced on us by being living things. This is not to say it is good or bad, but it does seem to provide a perspective that is more open to varying degrees of altruism, because upon regaining the sense of self, one does not find themselves as isolated from others. The idea that we are all one stream of consciousness is not appealing to me, because we do not share brains, regardless of how connected we are through evolutionary factors emphasizing our social nature.
Without the relationship between the self and the environment being established, things seems to blur. Life is a comparison to other things; it is relational. for example, take the adjective, 'strong.' Can one be strong if they are the only one explicating the idea of strength? If only one being exists and they can pick up something that weights 1000kg, are they strong, or are they just what is? It seems to me that there would need to be at least one other being. And if that being could only lift 500kg, then the first would be strong, while the other would not. Life is similar, and when the feeling of separation falls away, so does the ability to compare any differences.
Well, that's my take! I am very open to more discussion regarding any of the claims I have made. I could very easily be mistaken and only think that we will grow through more scientific discoveries and philosophical debates that clarify what it is we are really trying to answer.