Ashtavakra Gita 18.42 -

Sage Ashtavakra wants the seeker’s intelligence to be sharper and more perceptive. Spirituality is a mento-intelligential pursuit. It always enhances inner sensitiveness and fineness. Self is the subtlest. To perceive it, intelligence has to be equally fine.

Deeper and loftier introspection alone makes intelligence finer and finer. In place of gross world objects, intelligence should probe into the subject realm, where object imprints are formed and displayed. Mind, thought, thinking substance, thinker, etc. are points for finer introspection; finally, existence and non-existence also.

There is a book on a table. You look at the table and say there is a book there. After removing the book, you look at the same table to say the book is not there. In both cases, you are looking at the table alone. Its surface makes you see the book’s presence and absence. Table is there always, whether the book is or is not. It is the substratum for the book’s presence and absence.

Likewise the Self always remains as the ground for the experience of existence and absence of existence. Is not mind there when thoughts are present or absent? Self is there during wakefulness and its display. It is equally there, when all of it vanishes in sleep.

Leave wakefulness and sleep. Abide in the substratum of both. All thoughts and concerns vanish and you become free, calm and full. The mind that is thought-full can also be thought-free.