Philosophy Classics: The Six Schools of Indian Philosophy

Thesis: The cosmos is built from two ultimate principles — pure witnessing consciousness, "spirit" (puruṣa), and the source of all material and mental activity, "nature" (prakṛti); liberation comes from the discriminating insight that the two are utterly distinct.

Sāṃkhya is one of India's oldest systems, traditionally ascribed to Kapila. Its revolution is to halve the world: spirit is motionless pure consciousness, which only "watches" without acting; nature, under the tension of the three guṇas (sattva/clarity, rajas/activity, tamas/inertia), evolves into the twenty-five principles. Human suffering springs from one root error — mistaking the witnessing spirit for the evolving body-mind. See through it, and spirit rests like a spectator while nature's play winds down on its own.

Sāṃkhya's "spirit" resonates strikingly with the philosophy of mind's "hard problem": it cleanly separates "the consciousness that observes" from "all the mechanisms observed (thought, emotion, the sense of self)" — precisely Chalmers's distinction between "experience" and "function." The "three guṇas" of evolving nature also approach a kind of compositional dynamics: one substrate, the myriad phenomena emerging from differing proportions. However refined the mechanism, that dimension which "watches" cannot be reduced to it.

Thesis: Yoga accepts Sāṃkhya's metaphysics but does not stop at theory — it offers an eight-limbed practical path to still the mind and restore the "seer" to its place.

Patañjali organized scattered practices into a system, complementary to speculative Sāṃkhya: Sāṃkhya states "what is," Yoga states "how to do." The fluctuations (vṛtti) of the mind (citta) are like wind stirring water, distorting the seer through appearances; through the eight limbs (aṣṭāṅga), from moral restraint to samādhi, the waves are stilled layer by layer until the seer beholds its own nature. Key insight: liberation comes not by acquisition but by subtraction — remove the obscuration and the true nature shines of itself.

"Stilling the mind's fluctuations" has a solid neural correlate: in deep meditation the default mode network (DMN) markedly quiets, and the DMN is precisely the seedbed of self-narrative and rumination — almost a modern image of "citta-vṛtti cessation." Two millennia earlier Yoga noted that attention is trainable: the progression from concentration (dhāraṇā) to meditation (dhyāna) maps onto the gradient of today's attention-regulation research.

Thesis: Liberation begins with correct knowledge; and the reliability of knowledge depends on the "means" (pramāṇa) you use — whether the four valid means hold: perception, inference, comparison, and testimony.

Nyāya is India's stronghold of logic and epistemology, gripping one root question: on what grounds do you say you "know"? It establishes four valid means of cognition — perception (pratyakṣa), inference (anumāna), comparison (upamāna), and credible testimony (śabda). Its "five-membered syllogism" is distinctive: thesis (this hill has fire), reason (because it has smoke), example (as in a kitchen), application, and conclusion. Unlike pure Western deduction, Indian inference must anchor to a real "example"; logic stays rooted in experience.

At the heart of the syllogism is "pervasion" (vyāpti) — the universal concomitance "wherever there is smoke, there is fire," the lifeblood of all inference. Tellingly, Nyāya insists inference cannot do without an example (dṛṣṭānta), which brings it closer to induction and example-based learning than to pure formal deduction — structurally akin to machine learning's "learning rules from samples": reliable generalization rests on invariable concomitance supported by observed instances.

Thesis: Only "Brahman" is real, the phenomenal world is "māyā" (illusory appearance), and your inner "Self" (ātman) is not different from Brahman; liberation is to dispel ignorance through knowledge and recognize this primordial identity.

Grounding himself in the Upaniṣads, Śaṅkara stands opposed to Sāṃkhya's dualism: reality is not two, but one. He distinguishes two levels of truth — the absolute (the ultimate reality of Brahman) and the conventional (the relative reality of everyday experience): a rope mistaken for a snake in the dark — the snake is not truly there, yet not wholly nothing; that is "māyā." Likewise, mistaking the one Brahman for a teeming "self and world" is ignorance. Key insight: liberation is not to "become" anything, but to recognize the Brahman you have always already been — "That thou art."

Non-dualism's "two truths" echo neuroscience's "controlled hallucination": the everyday "I" and "external world" are not ultimate givens but stable representations the mind constructs upon some undivided substrate — Śaṅkara's "rope and snake" is just the classical version. A caveat: non-dualism points to a monism of consciousness itself, not physical reduction, sharing with Yogācāra's "mind-only" an Eastern consciousness-monist path.