Nyaaya system by Rishi Gauthama is the science of debate and discussion with reasoning and arguing. Logic is only a part of the Nyaya. It tells that knowledge implies four conditions: (i) the subject or Pramaata, (ii) the object or Prameya, (iii) the resulting state of cognition or Pramiti and (iv) the means of knowledge or Pramaana. Nyaaya says that the actions of man produce their fruits called adrishta which is supervised and controlled by God. God does not alter the course of adhrishta but renders its operation possible as the bestower of fruits of action. The cause of bondage is ignorance (Ajnaana). Twenty-one kinds of pain constitute bondage. Isvara has Eternal knowledge or nithya-jnana, who also has desire- action (Icchaa-Kriya) as qualities or gunas. He is all-pervading or Vibhu. False knowledge or mithya-jnana is the root of all misery and pain. It leads to the faults of likes and dislikes and proceeds to karma or action, good or bad. This forces a man into repeated cycle of birth as reward or punishment. Moksha is the destruction of pain and bondage. One gets the release and attains supreme felicity by realizing true knowledge of the Aathman.

Vaiseshika system by Rishi Kanada arranges its inquiries into categories (padarthas); such as substance, quality, action, general and particular property and non-existance. The knowledge of padartha is the means of attaining supreme good, resulting from the knowledge by a particular dharma. Sage Kanada does not openly refer to God in his suthras. The formation of the world was the result of adhrishta, the unseen force of karma or actions. The followers of Kanada introduced the concept of God as the efficient cause of the world. The atoms are the material cause of this universe. The body is subtle in pralaya and gross in creation. The time, place and circumstances of birth, family and life span are all determined by adhrishta. Conjunction of soul with body is called birth, disjunction is death and moksha is the non-existance of the conjunction with body, no potential body existing. Pleasure and pain result from the contact of soul, sense, mind and object. Desire and infatuation or moha arises from pleasure and aversion or hatred arises from pain. Intuitive knowledge of the Self destroys false knowledge. Consequently, all faults of moha will vanish.

In Saankhya system by Rishi Kapila, there is no analytical inquiry into the universe. There is a synthetical system starting from a primordial principle or thatthva called Prakrithi which evolves and brings forth everything else. Perception, inference and right affirmation are the three proofs on Sankhya. Prakrithi is eternal, has no cause but is the cause of all effects. It is crude matter without form. Prakrithi creates only when it comes in contact with Purusha. This is done for the emancipation of each soul. They bind the soul with a triple bond. Prakrithi is composed of the three gunas. All objects are composed of the three gunas, Sattva, Rajas and Tamas and their interaction leads to evolution or manifestation. All objects and actions are made of two ultimate realities, Purusha and Prakrithi. Purusha is without beginning or end and without attributes or qualities and are infinite in number. Bondage belongs to only Prakrithi and Purusha is eternally free.

The Yoga system, founded by Pathanjali Maharishi, is a branch or supplement to Sankhya. Yoga is restraint of the activities of the mind and is the union of the individual soul with the Supreme Soul. Pathanjali's Yoga is Raja yoga or ashtanga yoga which deals with discipline of the mind and its psychic powers. Hatha yoga deals with methods of bodily control and regulation of breath. Its culmination leads to Raja Yoga. In Kapila's Sankhya there is no Ishvara or God. In Pathanjali's `Yoga', there is a special Purusha or Ishvara. It accepts the metaphysical view of the Sankhya system, but it lays emphasis on the practical side of self-discipline and concentration of will power for the realization of the absolute unity of the Purusha. It claims greater orthodoxy than Sankhya by acknowledging the existence of a Supreme being or Ishvara. He is a special Purusha or a particular Soul unaffected by afflictions, works, fruition and vehicles. It describes the ethical discipline of Yama and Niyama, certain virtues to be followed, [see lesson 93] and the chief of them is nonviolence or ahimsa. Avidhya is the main cause of our troubles that leads to ego, desires and aversion that veils the spiritual vision. Devotion to God gives freedom.