True Self is the Self that existed before the division of heaven and earth and before one's father and mother were born. This Self is the Self within me, the birds and the beasts, the grasses and the trees and all phenomena. It is excatly what is called 'Buddha Nature".
This Self has no shape or form, has no birth, has no death. It is not a Self that can be seen with the aid of your present physical eye. Only the (hu)man who has received enlightenment is able to see this. The (hu)man who does see this is said to have seen into her own nature and became a Buddha. It is to use neither thought nor reasoning and to look straight ahead.
Source: The Unfettered Mind - Writings of the Zen Master to the Sword Master by Takuan Soho (1573-1645), P81 (Translation)
Contributed by: mita