Metaphysics: The Charvaka admits the existence of four elements — earth, water, fire and air — only and he rejects the fifth, the ether, because it is not perceived but inferred. Similarly, soul and God and the Hereafter are rejected.
Everything which exists, including the mind, is due to a particular combination of these four elements. The elements are eternal, but their combinations undergo production and dissolution. Consciousness is regarded as a mere product of matter. It is produced when the elements combine in a certain proportion. It is found always associated with the body and vanishes when the body disintegrates. Just as the combination of betel, areca nut and lime produces the red colour, or just as fermented yeast produces the intoxicating quality in the wine, though the ingredients separately do not possess either the red colour or the intoxicating quality, similarly a particular combination of the elements produces consciousness, though the elements separately do not possess it. Consciousness is the result of an emergent and dialectical evolution. It is an epiphenomenon, a by-product of matter. Given the four elements and their particular combination, consciousness manifests itself in the living body. ‘Matter secretes mind as liver secretes bile. The so called soul is simply the conscious living body. God is not necessary to account for the world and the values are a foolish aberration. Sadananda in his Vedantasara mentions four different materialistic schools. One identifies the soul with the gross body ( sthula sharira ); another with the senses ( indriya ) ; another with vital breaths ( prana ) and the last with the mental organ ( manas ). All the schools agree in regarding the soul as a product of matter. Shantaraksita says that the materialist Kambalashvatara maintains the view that consciousness arises out of the material body associated with vital breaths.
Severe and contemptuous criticism has been levelled against this doctrine by all schools of Indian Philosophy. If consciousness means self-consciousness as it means in the human beings, then it cannot be identified with the living body. The animals also possess the living body, but not rational consciousness. The Charvaka replies that it is a particular combination of the elements which obtains only in the human body that produces consciousness and that therefore living human body and consciousness are always associated together and nobody has seen consciousness apart from the living human body. But the argument is wrong. If consciousness is an essential property of the human body, it should be inseparable from it as the Charvaka claims. But it is not. In swoons, fits, epilepsy, dreamless sleep etc. the living body is seen without consciousness. And on the other hand, in dreams, consciousness is seen without the living body. When a dreamer awakes, he disowns the dream-body but owns the dream-consciousness. The dream-objects are sublated in the waking life, but the dream-consciousness is not contradicted even in the waking life. When a person gets up after seeing a tiger in a dream, he realizes that the tiger is unreal , being only a dream-tiger, but the fact that he saw a tiger in a dream remains a fact even in the waking life. This proves that consciousness persists through the three stages of waking life, dream life and deep sleep life and is much superior to material body which is its instrument and not its cause. Moreover, the subject, the knower cannot be reduced to the object, the known, since all objects presuppose the existence of the subject. Again, the subject is the enjoyer and the object is the enjoyed and the two cannot be identified. Again, the mere fact that consciousness is not experienced without the material body , is no argument to prove that it is a mere product of matter. The eye, e.g., cannot see in darkness. Sight is not possible without light, yet light cannot be regarded as the cause of sight. Mere co-existence is not causation. The two horns of a bull which are always found together cannot be regarded as causally related. The body is a mere instrument for the manifestation of consciousness and cannot be regarded as its cause. Moreover, if consciousness is a property of the body, it must be perceived like other material properties, But it is neither smelt nor tasted nor seen nor touched nor heard. Again, if consciousness is a property of the body, then there should be no consciousness of the body, for why should the body, qualified to produce consciousness, itself stand in need of being manifested by consciousness? Further, if it is a property of matter, then like other material properties it should be known by all in the same manner and should not be private. But we find that consciousness is intimately private and consciousness of an individual cannot be shared by others. Again, if the existence of the soul surviving death cannot be demonstrated, its non existence too cannot be so demonstrated.