In the seminal work by David Hume, A Treatise of Human Nature, we find he has penned this,
"When I enter most intimately into what I call myself...I can never catch myself at any time without a perception, and can never observe anything but the perception".
We may respond to this in a few ways.
1 - he must be a self for there has to be something there, something to experience the perception. An eye cannot conclude it cannot exist for it always sees something but not itself. He makes a category error. His self is the observer. It is not the observed. The self is what unifies your experiences as if one being, you is having them and knows this. The self is not about being observed but observing.
2 - not finding the self does not tell us if there is or is not a self. There could be a cat in the garage despite your inability to find it.
3 - he cannot find the self therefore there is no self
Buddha would have loved what Hume wrote.
He too decided that there is no reason to think there is a me.
If the self is an error or we don't know if it is or not then the following is false.
The Christian doctrine that I am a spiritual self so there might be a God who is also a spiritual self.
That God created me and loves me.
That Jesus had a self and came to save me.
From the fact that the mind lies to you about your past, how each memory is not an exact match for what really happened, we see that we only trust the present because we have to. The information cannot be trusted but to get on with life we trust it anyway. For that reason the self and lies unify your experience. Over time you change into somebody else. Any unifying that comes from lies and errors only works for a while and is not the best. It just happens to last long enough for life to go on. It is not real unity.
On the subject of your self as a self-conscious being, Flew in Appendix A of There is a God, suggested a thought experiment. Imagine a marble table. Could it become conscious and self aware and aware of its surroundings given virtually infinite time? His answer is that it has no properties for that to happen. Christians argue something similar when they say that the material and the physical cannot give rise to a self-aware living being.
If a soul is something that is non-physical and the physical itself is a mystery then why not? You can say you don't really know all about its properties. If even things have souls then why can't those souls come to life?
And it could become aware of itself even if not aware of what is around it.
If the self is a material physical thing then the spiritual self is not real. If you show you have a self that is as far as you can go. You cannot say what it is. And why would you want to? Religion wants you to for its own conniving reasons. Instead of body and soul we should talk brain and soul if we are religious. Why? Because your brain can be kept alive while your body is destroyed so the body hardly counts much. It counts even less if the brain itself is not really you, if you are a spirit in the brain. The brain does not really matter either then. But body and soul gives too much importance to the body when the brain with its soul is enough. So brain and soul it is.
If your self was an incorporeal spirit, then if your brain is removed from your body which is kept alive, and transported millions of miles away, then what? The spirit would go where the brain goes. Nobody likes the body degraded. To make you the real you is not your physical body is to call the body a mere costume or tool.
But then you may think, "Sure if your brain is the real you not the body you have the same problem."
Yes that is bad dualism too. But at least we are not making it worse by saying you are something special and non-material, a soul.
There is a difference between saying you are your physical brain but not your body and saying that you are your soul and not your brain or body. Your body becomes mere remains even if it is still alive no matter how you are you, if you are a soul or not. Saying there is a soul rubs this tragedy in. It is bad enough thank you.
The brain being you is nobody's doing or fault. But the soul thing would imply God is accountable.
Let us talk about feelings. Whether it is an illusion or not, you feel that you are something in your skull. How you will feel present where your brain is present is a degrading of the body. It says you are your brain and not your body. It is a form of dualism.
FINALLY
Dualism as in thinking the mind and body are separate with the mind being better and dualism as in feeling something like that are different. Both are damaging.
Hume's argument goes too far and there are better ways to overthrow personal identity. We conclude that there is a self but not a fixed one. And there is no reason to stress that it is ultimately a spiritual or non physical self.