What makes the Hindu knowledge system unique is the study of consciousness. We have the most comprehensive science of consciousness. After realizing that phenomenal world is relativistic, the next stage is realizing that the truth in phenomenal world is determined by state of consciousness of the observer. There begins the study of consciousness. Thus the study of consciousness is an advanced stage in man's pursuit of Truth.
Hindu science of consciousness deals with consciousness at all the levels, human, supra-human and sub-human. It expounds the various levels of consciousness, states of consciousness, the nature of consciousness at each level, the nature of Truth at each level of consciousness and methods to attain those levels.
Lokas (planes of consciousness)
The various planes of consciousness are called lokas or worlds. There are fourteen worlds, seven adho lokas (lower) and seven urdhva lokas (higher). Earth (physical consciousness) is at the bottom of urdhva lokas. The worlds below it are subconscious.
The seven urdhva lokas are bhuh, bhuvah, suvah, mahah, janah, tapah and satyam. These can be grouped into three, human-the interconnect-superhuman. Bhuh-bhuvah-suvah is the matter-life-mind triplet. Bhuh is earth or physical consciousness. Bhuvah is vital consciousness. Suvah is the world of mind. Mahah is the world of pure idea, thus it is also called vijnana loka. This is the plane where man begins transcending from personal to impersonal consciousness. The principle of manifestation can be understood through mahat, a higher function of intellect. Janah is the world of bliss, ananda. Tapah is the world of penance, chit. Satya loka is the world of Truth. The three higher worlds are sat-chit-ananda, the famous triplet of Truth-Permanence-Beauty or Existence-Consciousness-Bliss.
We find the mention of three worlds in the samhita, Bhuh, Bhuvah and Suvah. Indra is the lord of the swar/suvah world. But we find the explicit mention of the seven worlds in Taittireeya Aranyaka .
Kosas (sheaths of consciousness)
In parallel, a man is said to live in five sheaths of consciousness. These also called the panca kosas. The outermost is Annamaya Purusha, the physical man living in Annamaya kosa. Within it, sustaining it and sustained by it is Pranamaya Purusha, the vital man. Within it is Manomaya Purusha, the mental man or man living as a pure mind-being. Within it is Vijnanamaya Purusha, the man living in the world of pure idea. Within it is Anandamaya Purusha, the blissful-being. Within these five sheaths or kosas is said to live the eternal being, the Primal Purusha. By training himself to looking inwards and transcending the outer sheaths of consciousness one can realize the eternal being.
Bhrigu valli of the Taittireeya Upanishad expounds the five kosas. Bhrigu seeks the knowledge of Brahman from his teacher and father Varuna. Varuna asks Bhrigu to know the Brahman through penance. Bhrigu knows Anna to be Brahman and comes back. He is again sent to know Brahman through penance. Bhrigu goes repeatedly to know Brahman through penance and he successively discovers anna, prana, manas, vijnana and ananda to be Brahman respectively. That is, he discovers all these sheaths. Finally he realizes that ananda (Bliss) is Brahman. In this sheath (anandamaya kosa) lies the sat-chit-ananda (Brahman).
Lalita Sahasranama of the Brahmanda Purana praises the Godess as "panca kosantara sthita", the one who resides within the five kosas. The sahasranama is also called Yoga sahasra, the compendium of entire yoga and the study of consciousness.
Avasthas (states of consciousness)
The Mandukya Upanishad in Atharva Veda expounds the states or avasthas of consciousness. There are four states in which man perceives the world, jagrut (waking), swapna (dream), sushupti (dreamless sleep) and turiya (the fourth state).
In the waking state, the being called Vaisvanara, is outwardly cognitive and perceives gross objects. In the dream state, the being called Taijasa, is inwardly cognitive and perceives subtle objects. In dreamless sleep, the being called Prajna, is blissful, opening up to Soul-consciousness. The being in this state is and perceives the causal world.
Turiya, is neither inwardly nor outwardly cognitive nor non-cognitive. It pervades all states of consciousness and not any one of them. It is neither a combination of those nor void of those. All the other states and all phenomena dissolve in it. It is Brahman, the Absolute.
Lalita sahasranama praises the Godess as "supta prajnaatmika turya sarvavastha vivarjita", the one that is all the three states and the one beyond the states.
Faculties of Mind
There are four faculties of mind - mind-proper (Manas), intellect (Buddhi), ego (Ahankara) and memory (Chitta). Manas is the base of all mental cognition. All emotions, thoughts and impressions originate and manifest here. Buddhi is intellect. Discrimination, discerning and judgement are the functions of Buddhi. Ahankara is the sense of "I" or ego, which is the source of all action at mind-life-matter. Chitta is the impression of past experiences or memory.
Faculties of Soul-Consciousness
There are four faculties of Truth-Consciousness (Atma Chaitanya) too - intuition, inspiration, discrimination and revelation. Inspiration is the source, intuition is the means, discrimination is the judge and revelation is the destination in the seeking of Truth. The Veda treats these faculties as god-forms. Sarama is intuition, Saraswati is inspiration, Dakshina is discrimination and Ila is revelation. The Veda contains allegories to suggest these, like Sarama searching and finding the herds of revelation/dawn .
Levels of concentration
There are five levels of concentration, dispersed, restless, concentrated, stopping of mental activity and the experience of absolute. These are called Kshipta, Mudha, Vikshipta, Ekagra and Niruddha respectively.
An untrained mind is dispersed, with no specific object of thinking. It becomes restless when it is being trained to think on a specific object. Slowly it begins to concentrate on an object. This is the state of concentration. Beyond this when trained to concentrate on the formless, and sometimes also due to purification of mind in concentrated state, one will be able to stop mental activity and open up to soul-consciousness. This state is called chittavritti nirodha. In this state however outward objects exist, while the being is fully trained in inward-looking. This is the Praajna state described by the Mandukya Upanishad.
Beyond this state one can experience the absolute or Brahman. All the other states and phenomena are dissolved in this state and one experiences the one without the second. This state is called Nirvikalpa or Turiya-avastha.
There are three qualities or gunas, Satwa, Rajas and Tamas. Tamas is darkness, inertia. Rajas is inspiration, the force of action, creation. Satwa is knowledge, nobility, sustenance. The phenomenal world is said to be the play of these three qualities. The fourth, the one beyond the three qualities is called Trigunaateeta or the absolute.
Lalita sahasranama praises Godess as "trigunatmika" as well as "nistraigunya", the one having the three qualities and also the one beyond qualities.