I think this song is about realizing from looking at a picture of himself drunk that he is not real. An "exit does not exist", because he doesn't believe in an afterlife, which means that once you die there is nothing. He then realizes that if there is nothing when you are dead how can there be anything when you are alive, which is why he says "you don't even actually exist". The notion of being self aware or having a sense of "I" or "me" is just an illusion brought on by complex chemical and physical reactions in the brain in order to fill your role in the ecosystem.
I think this song is about realizing from looking at a picture of himself drunk that he is not real. An "exit does not exist", because he doesn't believe in an afterlife, which means that once you die there is nothing. He then realizes that if there is nothing when you are dead how can there be anything when you are alive, which is why he says "you don't even actually exist". The notion of being self aware or having a sense of "I" or "me" is just an illusion brought on by complex chemical and physical reactions in the brain in order to fill your role in the ecosystem.