To get to someplace on time, the decision to remove all other distractions to go anywhere else must be in place. In the same way to realise our self, we must withdraw from the distractions of indulging in other thoughts that do not pertain to the self. In the Vivekachoodamani, Sri Adi Sankaracharya shows what all thoughts that need to be negated or ignored if one is seeking after self-realisation.
The objects, people and circumstances that are listed to be on the negating chart are not the self. The first on the list is the very body that the self inhabits for a considerable number of decades during a lifetime i.e. this life. This body is made up of food and is the home for food.
The body is sustained with life by food and when the right food is not given in the right quantity at the right time, the body perishes. It is a conglomeration of skin, epidermis, flesh, blood, bones and excretory matter. While the self is eternal and pure, the body is born and dies in time, and it is a combination of much impure stuff. So it cannot be the self and hence has to be cut out of this list of self. Further, this body has no existence before birth and after death. Its very nature from the moment of birth is change and its qualities too keep changing moment to moment.
This body is not one thing like the self, it is a combination of many things. Like a pot, by itself it has no life in it and is an object of perception. The self is life itself, it is one and cannot be seen like an object. How then can the body be the self, which is observing the changes of the body? When I am able to observe the movement of a car from point A to point B, the car has to be different from me because I perceive the change points of movement of the car.
The body is not the self for yet another reason. It has parts such as hands and legs and even in situations when those parts are absent, the life continues to exist. While the limbs of the body are controlled by the self, it cannot be the very self which controls it. The controller and the controlled are two different things.
The self is the witness of the qualities of the body such as fatness, thinness, tallness, shortness, darkness or lightness. It is the witness of the actions such as seeing, tasting, smelling, touching and hearing, walking, talking or grasping. The self, which is evident by its own presence, is different from the body, which basks in the light of the self alone!