The Sanskrit word for a school of philosophy is darshana, "a seeing" or "a viewpoint". The same word is used when you go to a temple and stand before the deity: you have taken darshan. The choice of word is telling. A Hindu philosophy is not meant to be a set of opinions to argue about but a way of looking that, if adopted, lets you see something real.
Classical Hinduism counts six such viewpoints as astika, meaning those that accept the authority of the Vedas (the Buddhist, Jain and materialist schools are the nastika, those that do not). The six were never six sects; a single scholar might study all of them, and they argued with each other for well over a thousand years. They are usually taught in pairs, because each pair shares a basic picture of the world and divides the labour of explaining it.
Nyaya and Vaisheshika: logic and the furniture of the world
Nyaya, "the method" or "reasoning", founded on the Nyaya Sutras attributed to Gautama, is the school of logic and the theory of knowledge. Its central question is: how do we know anything? Nyaya answers with four pramanas, valid sources of knowledge: perception, inference, comparison, and the testimony of a reliable source. Every later Hindu school borrowed this toolkit, even when they disagreed about the list. Nyaya also formalised the five-step argument of Indian debate: there is fire on the hill, because there is smoke; wherever there is smoke there is fire, as in a kitchen; and there is smoke on the hill; therefore there is fire.
Vaisheshika, from vishesha, "particularity", founded on the sutras of Kanada, asks instead: what is the world made of? Its answer is a catalogue. Reality sorts into categories: substance, quality, action, universal, particular, inherence and, added later, absence. Physical substances are built from eternal, indivisible atoms that combine into pairs and triads, while time, space, selves and minds are substances of another kind. Vaisheshika is the closest thing ancient India had to a natural philosophy.
The two schools merged in practice. Nyaya supplied the method, Vaisheshika the inventory, and together they argued against the Buddhists that the world is real, plural and knowable, and that an eternal God can be inferred as its maker.
Samkhya and Yoga: the two realities and the way between them
Samkhya, "enumeration", is among the oldest of the six, and its basic picture underlies the Bhagavad Gita, the Puranas and Ayurveda. It asks: why do I suffer, and what am I apart from my suffering? Its answer is a sharp dualism. There are two kinds of reality. Purusha is pure consciousness, the witness, countless in number, never acting, never changing. Prakriti is nature, one, unconscious, endlessly active, made of three strands called the gunas. Everything we ordinarily call "me", the body, senses, mind, intellect and even the sense of ego, belongs to prakriti. Suffering arises because purusha mistakes the show of prakriti for itself, like a spectator who forgets he is not on the stage. Liberation, kaivalya, is the witness standing apart. Classical Samkhya needs no God for this account, and does not include one.
Yoga, the school of Patanjali's Yoga Sutras, accepts the whole Samkhya picture and asks the practical question: how, exactly, do I stop the mistake? Its answer is the eightfold discipline, from ethical restraints through posture and breath to meditation and absorption, by which the mind's movements are stilled until the witness is seen as witness. Yoga differs from Samkhya in one notable respect: it admits Ishvara, the Lord, described as a special purusha untouched by affliction and karma, and makes devotion to him one route to the goal.
Samkhya is the theory; Yoga is the laboratory.
Mimamsa and Vedanta: the two halves of the Veda
Mimamsa means "investigation", and in full it is Purva Mimamsa, the investigation of the earlier portion of the Veda, the hymns and ritual texts. Founded on Jaimini's sutras, it asks: what ought I to do? Dharma is whatever the Vedic injunctions enjoin, and the Vedas are reliable because they are eternal and authorless, not composed by any god or sage. Mimamsa developed detailed rules for interpreting commands, later drawn upon by Hindu jurisprudence, and argued that rituals work through an unseen potency, apurva, generated by correct performance. In its classical form it had little use for a creator God: the ritual works because the Veda says so. Its two branches, those of Kumarila and Prabhakara, differed on details but shared this focus.
Vedanta, "the end of the Veda", or Uttara Mimamsa, investigates the later portion, the Upanishads. It asks: what is the self, and what is its relation to Brahman, the ultimate reality? All its branches work from the same three foundations: the Upanishads, the Bhagavad Gita and the Brahma Sutras of Badarayana. They differ in how they read them.
- Advaita, non-dualism, systematised by Shankara around the eighth century: the self and Brahman are one; the appearance of difference, and of the world as independently real, is due to ignorance; liberation is knowledge.
- Vishishtadvaita, qualified non-dualism, taught by Ramanuja in the eleventh and twelfth centuries: Brahman is one, but selves and the world are real attributes or "body" of Brahman, as a body is to its soul; liberation is loving union with Vishnu, in which the self remains itself.
- Dvaita, dualism, taught by Madhva in the thirteenth century: God, souls and matter are eternally distinct; liberation is service to Vishnu by his grace.
Vedanta is the school most Hindus mean today when they say "Hindu philosophy", but it reached maturity by absorbing Nyaya's logic, Samkhya's analysis of nature and Mimamsa's rules of interpretation.
One question, six answers
The quickest way to feel the difference is to ask all six the same thing: is there a God, and what is God for?
- Nyaya-Vaisheshika: yes, and he can be proved. The world is an effect, and effects need an intelligent maker who arranges the atoms and assigns the fruits of karma.
- Samkhya: the question is not needed. Prakriti unfolds by itself for the sake of purusha, and liberation is discrimination, not grace.
- Yoga: there is a Lord, the perfect purusha, and devotion to him is a direct method for stilling the mind, though not the only one.
- Mimamsa: the gods named in the Veda are real as objects of ritual, but no creator is needed to make the ritual effective; the eternal Veda is the authority.
- Advaita Vedanta: Ishvara is Brahman seen through the lens of the world, real and worthy of worship, but at the highest level there is only the one Self.
- Vishishtadvaita and Dvaita: God is the supreme Person, Vishnu, with whom the soul's eternal relationship is the whole point of existence.
Six viewpoints, and each would say the others have seen something but not everything.
Why keep six
Why did the tradition not simply pick a winner? Partly temperament: the logician, the naturalist, the meditator, the ritualist and the mystic are all Hindus, and each found a darshana that honoured their way of seeing. Partly method: the schools sharpened one another, and much of what is best in each was forged in argument with the rest. And partly the word itself. A darshana is a seeing, and the tradition has always suspected that reality is large enough to need more than one.
To reflect on
Pick the question above that you find yourself asking most often: how do I know, what is the world made of, why do I suffer, what should I do, what am I? That question is your natural doorway. Read one short primary text of that school, slowly, and see whether its way of seeing changes anything you look at this week.