The six darśanas — why they argue, not agree
Western introductions to Indian philosophy often flatten the six schools into one big 'Hindu worldview'. They are not one worldview. They are six arguments.
There is a kind of introductory book — and a kind of introductory YouTube video — that presents Indian philosophy as if it were a single mushy blob of 'Eastern wisdom'. Everything in it flows, everything is connected, everything is ultimately one. This is almost exactly the opposite of what Indian philosophy actually looks like in its source documents. It is, in fact, a two-thousand-year argument among people who took argument so seriously that they argued across lifetimes.
The argument has a shape. Classical Hindu philosophy recognises six darśanas — six 'seeings' — that accept the authority of the Vedas. They are Nyāya, Vaiśeṣika, Sāṃkhya, Yoga, Mīmāṃsā, and Vedānta. They are traditionally paired — Nyāya with Vaiśeṣika, Sāṃkhya with Yoga, Mīmāṃsā with Vedānta — because each pair works at similar problems from complementary angles. Outside these six stand the Śramaṇa schools: Buddhism, Jainism, Cārvāka, Ājīvika, and later tantric and bhakti traditions. All of them talk to each other, and most of them disagree with each other, and the disagreements are not polite. If you read the classical commentaries, the rhetoric can be startlingly sharp. Śaṅkara spends hundreds of pages demolishing positions. Rāmānuja spends hundreds of pages demolishing Śaṅkara. A thousand-year debate is continuous.
What are they arguing about? Four big things, mostly.
How do we know anything? This is the pramāṇa question — the theory of valid knowledge. Nyāya says there are four sources of valid knowledge: perception, inference, analogy, and verbal testimony. Vaiśeṣika adds atomism. Sāṃkhya and Yoga accept three. Mīmāṃsā accepts six. Advaita Vedānta eventually agrees with Mīmāṃsā's six. The Cārvākas — the Indian materialists — accept only perception, which turns out to be a fighting position. This is not trivia; the entire argumentative structure of the rest of the system depends on what you accept as valid knowledge.
What is there? This is the ontology question. Sāṃkhya says reality has two kinds of stuff: puruṣa (pure consciousness) and prakṛti (active nature). They never mix. Everything we see is prakṛti moving; consciousness is just the witness. Advaita Vedānta says reality is one stuff, brahman, and everything else is appearance. Viśiṣṭādvaita says reality is one stuff but it has real distinctions internal to it. Dvaita says reality is at least two stuffs and they are ontologically different. Buddhism says there is no stuff at all — just dependent origination, a process. Jainism says there are many kinds of stuff and they are all real. Tantra says the real stuff includes the body. The positions are not variants of each other; they are incompatible.
What is the self? Closely related to the ontology question, but worth separating. Vedānta says the self (ātman) is identical with brahman. Sāṃkhya says the self is puruṣa and is separate from all of prakṛti (including your personality, memories, intellect — those are prakṛti). Buddhism says there is no self at all; the search for one dissolves into dependent origination the moment you look carefully. Jainism says each self is eternal, individual, and plural. The Nyāya position is yet another thing. These positions produce different meditation instructions. They cannot all be right.
What is liberation, and how do you get there? Yoga says by stilling the mind. Sāṃkhya says by discriminating puruṣa from prakṛti. Vedānta says by seeing that you already are brahman. Buddhism says by seeing that there is no self to liberate. Bhakti says by loving God, who then takes care of the rest. Karma-Mīmāṃsā says by performing the prescribed rituals correctly. The routes differ, the destinations differ, and in some cases the existence of the destination is itself in dispute.
So what does it mean to call these schools 'orthodox Hinduism'? Very little. It mostly means they accept the Vedas as authoritative. What they do with that authority is wildly different. Mīmāṃsā reads the Vedas as a ritual manual — most of the 'meaning' is the ritual action, and questions about gods are secondary. Vedānta reads the Vedas as a revelation of the self — the ritual material is warm-up for the philosophical material at the end. These two schools are literally reading the same texts and disagreeing about what they say.
The point of introducing all this is not to overwhelm the reader with positions. The point is to offer a different picture of what Indian philosophy is — not a mushy consensus but a durable argumentative culture. That culture produced better philosophy than consensus would have. Consensus is where thinking goes to die. Sustained, rigorous, honest disagreement is where it grows.
When you read Indian philosophy seriously, you are not being initiated into a single worldview. You are being invited into a conversation, and you will eventually be expected to take sides. That is a much more demanding invitation than the introductory books admit. It is also a much more Indian one.