Existence of the Self
Advaita (non-duality) is the Vedanta school associated with the philosopher Sankara (c. 788 820 AD) who is acknowledged as the leader of the Hindu revival after the Buddhist period in India. Sankara's metaphysics are based on the criterion that the real is that whose negation is impossible.
From this criterion it follows that the self is real, because no one will say ‘I am not’ Sankara writes that: Just because it is the Self, it is impossible for us to entertain the idea even of its being capable of refutation.
The Nyaya-Vaisesika subscribe to the conception of the self put forward in the Vedas as a substantial, persistent and non-material entity. They agree with the Vedantins that the self can not be perceived, but only inferred. The later Nyaya school however rejected the idea that the self can only be known by inference and asserted that the existence of the self can be directly perceived. The idea that the self can be directly perceived is put forward by Udayana in a polemical work against the Buddhists.
The Nyaya argument for the existence of the self through the notion of agency: ‘From the actions of the mind towards the contact of the sense-organ apprehending desirable objects, we infer the existence of the self’
An analogy offered by the Nyaya is that from the action of regular breathing we infer the existence of the agent who would act like a blower of the wind-pipe. The Nyaya are clearly referring to intelligent actions and not merely mechanical actions like that of a robot for example.
The Carvaka argue that the self is nothing but the body as characterised by consciousness. The Carvaka denial of a substantial self is based on the epistemological position that perception is the only valid source of knowledge. The Carvaka deny the validity of inference and other sources of knowledge (darsanas) usually accepted in classical Indian philosophy. From this position and the Brahminical assertion that the self can not be perceived they infer that the self can not exist because only that which can be perceived exists.
This last premise is however not a fair representation of the Brahminical position because the Mimamsa and the later Naiyayikas insist that the self as the subject is directly cognised in every experience. In the available texts there is however no detailed discussion whether the Carvaka had any arguments to deal with the Mimamsaka and the later Naiyayikas.
The Buddhist reply to the Brahminical view of the self would be that there is no such entity. This view is illustrated by the debate between king Milinda and the Buddhist monk Nagasena. 9 King Milinda is not convinced of the theory of the notself for, ‘if there were no person, there could be no merit and no demerit …’
Nagasena clarifies the theory of the not-self to the king by comparing a human being with a chariot. Non of the individual parts of the chariot (the pole, the axel, the wheels etc.), are the chariot. Nor the combination of the parts is the chariot. Nagasena continuous that he can not discover a chariot at all, only the word that denotes the idea of the chariot. The denomination chariot or self takes place in dependence of the individual parts. In ultimate reality, the person can not be apprehended. Sankara takes issue with this theory, on the grounds that it provides nothing to hold together the various ingredients either at any one time or through progression in time