I understand that the witness is pure consciousness, and, untouched by the body and mind, it only temporarily resides in them.
So, firstly: how does the personality transfer its characteristic traits and conditioning from one life to another? And secondly: isn't this what makes us unique individuals, with the potential for growth?
Answer:
"Manisha, the first thing you must understand is that you have not only this body with its flesh, bones, and blood, not only this brain, which is part of your body. Inside your brain is hidden the mind – this is an abstract mind, and inside your body is hidden the astral body. The word 'astral' is related to the stars; it means light... This body radiates light, and it includes the mind.
When you die, you leave your physical body and physical brain. But your astral body travels with you, with the mind, with the memories of past lives, and with a body that remembers all the wounds and scars that your physical body has received. This abstract phenomenon travels with you, and deep within it is hidden your existential center.
Until you know the center, you will continuously travel from one body to another. You have already traveled through thousands of lives, the memories of which are stored in your astral mind, and there are more and more of them. And although your center is untouched, it is surrounded by the astral body, and this astral body passes from womb to womb, from grave to grave. This is your individuality, and it has a continuation. But the continuation will come to an end as soon as you become a Buddha.
When you penetrate deeply into the center, you also transcend your astral body; you go through the mind, beyond the mind, through the astral body, beyond it, to the center of your being. Once you penetrate it, the continuation of your individuality comes to an end. And then real life begins. You will never enter a womb again, and you will no longer be burned on a funeral pyre. Now you have become part of the whole."
Osho