Major Schools of Indian Philosophy (Astika and Nāstika) — Overview and Distinguishing Features

Indian philosophy, traditionally termed Darśana, categorizes classical schools of thought into two broad divisions based on their attitude toward the authority of the Vedas: Āstika (orthodox) and Nāstika (heterodox). This division does not strictly depend on a belief in God, but rather on whether a system accepts the divine authority and epistemological supremacy of the Vedic texts. The six orthodox systems, collectively known as the Ṣaḍdarśana, acknowledge Vedic authority, whereas the heterodox systems reject Vedic primacy and develop independent metaphysical and epistemological frameworks.

Classification Framework: Āstika vs. Nāstika

The formal division of Indian philosophical systems centers on three main criteria: acceptance of Vedic authority, belief in an immortal soul (Ātman), and belief in an afterlife or the law of Karma.

• Āstika (Orthodox) Systems: Accept the ultimate authority of the Vedas. These six systems comprise Nyāya, Vaiśeṣika, Sāṁkhya, Yoga, Mīmāṁsā (Pūrva Mīmāṁsā), and Vedānta (Uttara Mīmāṁsā). Some Āstika systems, such as Sāṁkhya and Pūrva Mīmāṁsā, do not mandate a creator God in their foundational stages, yet remain Āstika because they uphold Vedic authority.
• Nāstika (Heterodox) Systems: Reject the authority of the Vedas. The major Nāstika schools include Cārvāka (Materialism), Jainism, Buddhism, Ājīvika (Fatalism), and Ajñāna (Skepticism).

The Six Āstika Schools (Ṣaḍdarśana)

Sāṁkhya School

• Founder and Text: Founded by Sage Kapila; key textual authority is the Sāṁkhyakārikā by Īśvarakṛṣṇa.
• Core Philosophy: A dualistic realist system positing two ultimate, independent realities: Puruṣa (pure consciousness) and Prakṛti (matter/nature).
• Cosmic Evolution: Evolution begins when Puruṣa comes into proximity with Prakṛti, disrupting the equilibrium of the three Gunas (Sattva, Rajas, Tamas). This process yields 23 evolutes, forming a total of 25 Tattvas (categories).
• Theistic View: Originally non-theistic (Nirīśvara Sāṁkhya), asserting that the existence of God cannot be logically proven.

Yoga School

• Founder and Text: Formulated by Sage Patañjali in the Yoga Sūtras.
• Core Philosophy: Accepts Sāṁkhya dualism and metaphysics but adds a personal deity (Īśvara) as a supreme Puruṣa, earning the designation Seśvara Sāṁkhya.
• Practical Path: Outlines the Aṣṭāṅga Yoga (Eight-limbed path) for liberation: Yama (restraints), Niyama (observances), Āsana (posture), Prāṇāyāma (breath control), Pratyāhāra (withdrawal of senses), Dhāraṇā (concentration), Dhyāna (meditation), and Samādhi (absorption).

Nyāya School

• Founder and Text: Founded by Sage Gautama (Aṣapāda Gautama) in the Nyāya Sūtras.
• Core Philosophy: A school of logic, epistemology, and critical analysis. It holds that liberation (Apavarga) comes through attaining valid knowledge of 16 logical categories (Padārthas).
• Epistemological Contributions: Developed systematic rules for debate, syllogistic reasoning (Pañca-Avayava), and logical inference.

Vaiśeṣika School

• Founder and Text: Founded by Sage Kaṇāda (Ulooka) in the Vaiśeṣika Sūtras.
• Core Philosophy: A physicalist and atomistic system. It classifies reality into seven categories (Padārthas): Dravya (substance), Guṇa (quality), Karma (action), Sāmānya (generality), Viśeṣa (particularity), Samavāya (inherence), and Abhāva (non-existence).
• Atomic Theory (Aṇuvāda): Asserts that the physical universe consists of indivisible, eternal atoms (Aṇu) of four elements: earth, water, fire, and air, combined under the influence of an unseen moral force (Adṛṣṭa). It later merged closely with the Nyāya school.

Mīmāṁsā / Pūrva Mīmāṁsā School

• Founder and Text: Founded by Sage Jaimini in the Mīmāṁsā Sūtras.
• Core Philosophy: Focuses on ritual hermeneutics and the execution of Vedic duties (Dharma). It asserts that the Vedas are eternal, unauthored (Apauruṣeya), and infallible.
• Major Sub-Schools: Developed two major branches led by Kumārila Bhaṭṭa (Bhaṭṭa Mīmāṁsā) and Prabhākara (Prābhākara Mīmāṁsā), differing on epistemological details and the number of accepted valid proofs.

Vedānta / Uttara Mīmāṁsā School

• Founder and Text: Formulated by Bādarāyaṇas in the Brahma Sūtras (also called Vedānta Sūtras). It interprets the philosophical teachings of the Upanishads.
• Sub-Schools of Vedānta:
  • Advaita (Non-dualism): Propounded by Ādi Śaṅkarācārya. Posits that Brahman is the sole reality, the empirical world is Māyā (illusion), and the individual self (Jīva) is identical to Brahman.
  • Viśiṣṭādvaita (Qualified Non-dualism): Propounded by Rāmānujācārya. Asserts that the world and individual souls are real attributes or body of the supreme reality, Brahman (Vishnu).
  • Dvaita (Dualism): Propounded by Madhvācārya. Maintains a complete separation between God, individual souls, and matter.

The Nāstika Schools (Heterodox Systems)

Cārvāka / Lokāyata School

• Founder and Authority: Attributed to Sage Bṛhaspati; preserved through references in opponent texts.
• Core Philosophy: Radical materialism, hedonism, and empiricism. It rejects the soul, an afterlife, rebirth, karma, heaven, hell, and divine authority.
• Epistemology: Accepts direct perception (Pratyakṣa) as the only valid source of knowledge, rejecting inference (Anumāna) and verbal testimony (Śabda) as unreliable.

Buddhism

• Founder and Text: Founded by Siddhārtha Gautama (The Buddha). Core teachings are preserved in the Tripiṭaka (Pali Canon).
• Core Doctrines:
  • Four Noble Truths (Āryasatya): Life contains suffering; suffering has a cause; suffering can end; there is a path to end suffering.
  • Eightfold Path (Aṣṭāṅgamārga): Path leading to the cessation of suffering.
  • Anattā (Non-self) and Anicca (Impermanence): Denies an eternal, unchanging soul (Ātman) or substance.
  • Pratītyasamutpāda: The law of dependent origination explaining cosmic cause and effect.

Jainism

• Key Figures and Texts: Codified by the 24th Tirthankara, Vardhamāna Mahāvīra. Sacred literature includes the Āgamas.
• Core Doctrines:
  • Anekāntavāda: Theory of many-sidedness of reality.
  • Syādvāda: Theory of conditioned predication or seven-fold judgment (Saptabhaṅgīnaya).
  • Triratna (Three Gems): Right Faith (Samyak Darśana), Right Knowledge (Samyak Jñāna), and Right Conduct (Samyak Cāritra).
  • Jīva and Ajīva: Divides reality into conscious souls (Jīva) and non-conscious matter (Ajīva).

Ājīvika School

• Founder: Founded by Makkhali Gosāla during the 6th century BCE.
• Core Philosophy: Strict determinism and fatalism (Niyati). It holds that karma and human effort cannot alter human destiny or salvation, which unfolds through preordained natural cycles.

Ajñāna School

• Founder: Associated with Sañjaya Belaṭṭhiputta.
• Core Philosophy: Radical skepticism. It held that metaphysical knowledge is impossible to achieve and that taking definitive philosophical positions causes intellectual distress.

Epistemological Framework (Pramāṇas) Across Schools

Indian philosophy evaluates validity using recognized sources of knowledge (Pramāṇas). The number of accepted Pramāṇas varies across systems.

Core Facts on Indian Philosophy

• The word Darśana derives from the Sanskrit root Dṛś, meaning “to see” or “viewpoint.”
• The Sāṁkhya system recognizes 25 fundamental principles (Tattvas), where Puruṣa is the 25th principle.
• Sage Kaṇāda’s Vaiśeṣika system is considered the earliest formal proponent of atomic theory in Indian thought.
• The Nyāya school developed the five-membered syllogism: Pratijñā (proposition), Hetu (reason), Udāharaṇa (example), Upanaya (application), and Nigamana (conclusion).
• Cārvāka philosophy is also called Lokāyata, translating to “prevalent among the people.”
• The term Tīrthaṅkara in Jainism translates to “ford-maker” or one who establishes a passage across the ocean of worldly existence.
• The Ājīvika sect received royal patronage from Mauryan Emperor Ashoka and his grandson Dasharatha, who gifted them the rock-cut Barabar and Nagarjuni caves in Bihar.
• Śaṅkarācārya established four monastic centers (Mathas) at Sringeri (South), Puri (East), Dwarka (West), and Badrinath (North) to consolidate Advaita Vedānta.
• The Bhaṭṭa Mīmāṁsā school recognizes six Pramāṇas, accepting Anupalabdhi as the sole valid mean for perceiving non-existence.
• The Pratītyasamutpāda doctrine in Buddhism is depicted visually in the Bhavacakra (Wheel of Becoming) through twelve interconnected links (Nidānas).