This witness-state is called the Turiya or the fourth state of consciousness.
It is said that, as sweetness, liquidity and coldness, which are characteristics of water, appear as inherent in the waves, and then also in the foam, of which the waves form the background; existence, consciousness and bliss, which are the natural essences of the Atman, seem to inhere in the wakeful Jiva on account of its relation with the Atman. Likewise, these facets of the Atman are felt also in the dreaming self, by way of the impressions of the waking consciousness. And just as, on the disappearance of the foam, their characteristics, such as liquidity, revert to the waves, and, again, as with the subsiding of the waves in the sea, these exist in the waters of the sea as before; so existence, consciousness and bliss manifest themselves and shine in the waking consciousness after the disappearance of the dreaming state; and then, again, on the dissolution of the waking phenomena in the Atman, these eternal natures are experienced in the Atman, which is the highest reality. In Moksha, or the final liberation of the soul, when all objective perception is overcome in the consciousness of Brahman, even the character of being a witness drops from the self, and it realises its majestic independence.
Sometimes the states of consciousness are regarded as being sixteen in number. â€œThere are sixteen states of consciousness. They are made up as follows: There are the four primary states of consciousness, called Jagrat, Svapna, Sushupti and Turiya (waking, dreaming, deep sleep and the Witness-consciousness). These, by differentiation, multiply into sixteen states. These are Jagrat-Jagrat (waking in waking), Jagrat-Svapna (waking in dreaming), Jagrat-Sushupti (waking in sleep), Jagrat-Turiya (waking in super-consciousness), and so on with the remaining three other states. These sixteen states, by further differentiation, become two hundred and sixty-six states. These, again, by the differentiation of the phenomenal and the noumenal, become five hundred and twelve states. To realise these states of consciousness, it is very difficult, and is not possible for everyone.â€ â€œThat is called Jagrat-Jagrat, in which there are no such ideas as â€˜thisâ€™ or â€˜mineâ€™ regarding visible things. The great ones call that Jagrat-Svapna in which all ideas of name and form are given up. This is preceded by the realisation of the nature of Satchidananda. In the state of Jagrat-Sushupti, there is no idea but Self-knowledge. In Jagrat-Turiya the conviction becomes firm that the three states,â€”gross, subtle and causalâ€”are false. In Svapna-Jagrat there comes the conviction that even the activities proceeding from the astral plane, owing to causes set in motion previously, do not bind the self, when the knowledge of the physical plane is destroyed. In Svapna-Svapna there is no seer, seen and sight, when the Karana-Ajnana (ignorance which is the root of all) is destroyed. It is Svapna-Sushupti where by means of increased subtle thinking, the modifications of oneâ€™s mind get merged in knowledge. That is Svapna-Turiya, in which the innate bliss (pertaining to the individual self) is transcended by the attainment of universal bliss. That state is called Sushupti-Jagrat in which the experience of Self-bliss takes the shape of universal intelligence through the rising of the corresponding mental modifications. In Sushupti-Svapna one identifies oneself with the modifications of the mind which has long been immersed in the experience of inward bliss. When one attains oneness of knowledge (Bodhaikya), which is above these mental modifications and above the realisation of any abstract condition, one is said to be in Sushupti-Sushupti. In Sushupti-Turiya, Akhandaikarasa (the one undivided essence of bliss) manifests itself, of its own accord. When the enjoyment of the Akhandaikarasa is natural in the waking state, one is said to be in Turiya-Jagrat. Turiya-Svapna is difficult of attainment; it is a state in which the enjoyment of Akhandaikarasa becomes natural even in oneâ€™s dreaming condition. The still higher state of Turiya-Sushupti is even more difficult of accomplishment. In this state, the one undivided essence of bliss manifests itself to the Yogi, even in deep sleep. The highest state is Turiya-Turiya, wherein Akhandaikarasa disappears like the dust of the clearing nut (Kataka) used for clearing water. This is the Arupa or the formless state and is beyond cognitionâ€ (Vedanta in Daily Life, pp. 211-14). The Kaivalyopanishad says that the states of consciousness are appearances of one Brahman, and that one who knows this is freed from all bonds (Verse, 17).