--> What you say is true. But you make take it to its obvious conclusion -- I do not exist, you do not exist, this computer in front of me does not exist, etc. Nothing exists in the true sense of the word. Thus, there is no self -- or anything else
I think this is what scares people. The idea that nothing really exists, that it is just some projection of an infinite void, and there is no self. I've come to the same conclusion, that the universe is just existence. It is definitely mysterious though, there is some power that underlies it. However, it cannot be a personal god IMO.
If we said that Brahman or Nirvana, is the non-dual universe, where the observer and the object collapse into one, then this state is neither existence or non-existence, neither conscious or non-conscious. It is some peculiar state.
When in objectless Samadhi(meditation) the mediator experiences the same peculiar state, which lies beyond existence and non-existence. This state is called Maha Nirvana by Buddha.
Those that have experienced this ultimate state of existence, have called it Sat-Chit-Anand(Existence, Consciousness and Bliss) and Buddha called it Maha Nirvana. They are both describing it as a state of experience, not as an entity.
Now, I need to ask, how can there be consciousness and no self? We can only use the term "self" if there is duality. That is if there are two or more. If there is only one, then there is no self. For example, if we could only see one colour, we would not know what "colour" was If we could only feel cold, we would not know what temperature was. Self-awareness only comes into being when there is duality.
So what is consciousness, devoid of self. A conscious devoid of self, would be the experience of everything as one. Like an ocean, devoid of waves, exists as an ocean.
We will stay with the ocean example and each wave arising in the ocean is a part of that ocean, yet to an observer it would look as if the wave has a seperate existence, even though it is still the ocean, only a modification of it. So it is the modification that creates the duality. Now, let us suppose that the ocean is conscious. When a wave arises in the ocean, it is both conscious of the ocean, and also conscious of the modification(the wave) however as the wave is a disturbance in the non-dual nature of the ocean, the ocean is more aware of the wave, and begins to identify with it. Now the wave has self-awareness, it is an individual unit of consciousness, thus a soul. However, we know it really is only a modification, and the self-awarness is an illusion.
Now, because the wave is self-aware, there is duality, there is both subject and object. This is where objective existence begins, which has both the dimensions of space and time.
So when we think of ourselves as individual souls, we are just modifications of that consciousness, and our individuality is only an illusion. Each life is therefore a different modification, which means that one modification cannot be the other. This means I cannot be who I was in my past life.
In fact, it is such, that all of our lives, past, present and future belong to the same consciousness. If we model that consciousness as "I" then it means I have experienced every life and every possibility.
How does this fit into the reincarnation framework? Reicarnation, would be an order of modifications, the first modification is the "I'ness" and the soul comes into being, then it starts to evolve(the ascent of the wave) and takes on innumerable lives, but a certain sequence of lives. The sequence it takes, is unique to it. So no two souls can have the same past life.
As an ocean is comprised of many waves and each wave is different, likewise, consciouness takes on the form of many souls, and each soul is different, and follows a different path, until it starts to realise that it really isn't a soul, it is consciousness(the descent of the wave.)
So the existence of the soul, like all things, is relative, but like all relative things, the soul is transient and has a beginning, middle and end. Just like the wave in an ocean.
In Sankhya philosophy, all of this universe, including the souls, are all modifications of the Gunas(Rajas, Sattva and Tamas) which are three qualities(Attraction, Inertia and Balance)and in time these modifications resolve themselves, until there is only the Guna of Sattva. That is when the universe returns to it's original unmanifest state.
Likewise, the Gunas work on the individual level as well, our actions, thoughts and speech can either be Rajasic, Sattavic or Tamasic. When we concentrate on Sattavic, we begin to resolve the Gunas of Rajasic and Tamasic, until we are only Sattavic and we return to our true non-dual nature.
So what is really causing the modifications to arise, is when these three qualities or forces come out of their equilibrium.