There is but one reality and that is the self.
Everything is self.
There are, however, three ways to experience this reality.
One is to have a self and to be aware of the fact that you are a self.
Second is to have a self and to not know it.
Third is, of course, to not have a self.
The first is the ultimate goal or purpose of reality, to know the self.
The second, to have a self and not know it is the source of all suffering, sorrow, and pain.
It must be so in that the lost soul must come to know the self in order to ease its suffering.
Much like the pain of hunger must exist so that you will eat, the pain of separation of the true self felt by the ego-self must exist in order that we will seek out our true existence and remember who and what it is that we are.
The third, to not have a self means those objects which on their own cannot exist unless a self experiences them, such as chairs and stones, etc.
A cat, for example, has a self but lacks the intellect to know itself, many humans are afflicted in the same way.
They suffer yet do not know why.
It is because they are separated from true reality and no being can rest in peace until it is reunited with its true source, the self.
If one’s body fails while they still do not know the source, they die with the belief that they are the body.
In their panic, the first thing they do is to manifest themselves in another new body, and thus, the cycle of samsara (birth and death) runs its course until one awakens within the body.
The true knowledge and understanding of the self severs the connection to the body and clears the eyes of all delusions.
When one is then finished with the body it is discarded like a worn-out cloak.
That being is not connected to a body nor does it believe itself to be a body, therefore it feels no compunction to manifest itself in a new one.
This is Nirvana.
This is immortality.
This is enlightenment.
This is Zen.