Schools of Indian Philosophy: Orthodox & Heterodox Schools
Gajendra Singh Godara
Nov 7, 2025
12
mins read
Indian philosophy investigates fundamental issues concerning existence, reality, knowledge, obligation, and freedom. It includes various systems of thought, the two basic divisions in schools of Indian Philosophy are: Astika (orthodox) and Nastika (heterodox). Astika includes the six classical systems of Nyaya, Vaisheshika, Samkhya, Yoga, Purva Mimamsa, and Vedanta, as well as Nastika traditions which are Buddhism, Jainism, charvaka and Ajivika.
Philosophical traditions in the school deal with vital themes around
the self (atman),
the ethical order (rita),
duty (dharma),
the cycle of rebirth (samsara),
action and the consequences (karma), and
the liberation (moksha).
These along with the many other traditions have contributed to the flourishing erudition of the nation and enriched not merely the spirituality but also the culture and ethics of the people.
Classification of Schools of Indian Philosophy: Astika and Nastika
Astika (orthodox) and Nastika (heterodox) Philosophical Schools in India.
Astika schools accept the Vedas while Nastika schools do not.
Astika schools accept the rebirth of the self (atman) while Nastika schools deny the soul and the soul's rebirth (Charvaka) or follow Buddhism which teaches the soul is not permanent (anatman).
Astika philosophies accept the existence of gods or a moral order of the universe while Nastika schools believe in no creator god or gods (Carvaka denies all deities and Buddhism revolves around natural law).
Moksha is freedom from suffering and rebirth, and all schools seek it. However, each has its own means of achieving it (knowledge, devotion, practice, etc.).
This illustrates which tradition is Astika or Nastika and explains the main viewpoint of each school.
The Six Orthodox Schools of Indian Philosophy (Shad-Darshanas)
Indian philosophy is more than just abstract ideas. It is a complete system meant for engaging with life, the universe, and our place in it.
Indian scholars and sages have been developing ideas for thousands of years. They focus on six main philosophical systems called the Shad-Darshanas. The term is translated as “six viewpoints.”
Each of the philosophical systems conforms to the Astika category or orthodox systems, as they recognize the authority of the Vedas. Although there are variations in emphasis within the systems, with some focusing on reason or spiritual exercise and others on devotion, they all strive for the same ultimate goal, liberation or moksha.
Samkhya
Overview and Founder:
Kapila was the founder of the Samkhya darshan. It is one of the oldest philosophical traditions in India. It offers a dualistic view of the world, seeing reality as composed of two eternal principles : purusha (pure consciousness) and prakriti (matter or nature).
Core Philosophy:
All that exists in the universe is derived from prakriti which translates into 25 fundamental elements (tattvas). The state of liberation which is termed kaivalya is achieved in the realization of our true self (purusha) and that it is entirely distinct from the material world (prakriti).
Metaphysical View:
In Samkhya the world’s reality is a dualism of purusha and prakriti which is consciousness and matter. The intertwining of the two brings about all of the life experiences. The freedom of purusha is in recognizing its true nature and independence.
Yoga
Overview and Founder:
The Yoga school founded by Patanjali. It builds upon Samkhya’s ideas by “practice and discipline”. For Yoga, the “Yoga Sutras” is an attainable peace and self-realization guide.
Core Philosophy:
The Yoga school elucidates the “Eightfold path”, which consists of moral discipline, control and mastery of the body, breath, concentration, meditation and samadhi (deep state of absorption). It enables the individual to master the mind and the primal urges resulting in moksha (liberation).
Metaphysical View:
Like Samkhya, Yoga views the duality of purusha and prakriti. It emphasizes self control and meditation techniques to purify the mind to experience the separation of spirit and matter.
Nyaya
Overview and Founder:
Aksapada Gautama established the Nyaya school around the 6th century BCE. It is described as the “India’s systems of logic and reasoning”. It takes on the question of how one can “ know” something and the ignorance which is the root of all sufferings.
Core Philosophy:
Nyaya mentions four valid sources of knowledge or pramanas as follows:
perception,
inference,
comparison,
and testimony.
Corrupt beliefs can be shattered by true knowledge or prama and rational and clear thinking. Ultimately, this culminates in liberation.
Metaphysical View:
With realism as its foundation, Nyaya is based on rational metaphysics. The world is real and can be apprehended. It also takes the notion of God as the creator and the guide of the universe. Souls and atoms are regarded as eternal realities.
Vaisesika
Overview and Founder:
Kanada laid the foundations for the Vaisesika system which concerns the composition of reality. It constitutes one of the earliest forms of atomism – the doctrine which posits that the material universe consists of small, discrete, and indivisible particles.
Core Philosophy:
Vaisesika further expands and explains the various constituents of the universe and the relationships that obtain different forms of existence by positing that all things can be classified into one of the five categories (padarthas): substance, quality, action, generality, and particularity.
Metaphysical View:
Vaisesika posits that the world consists of eternal atoms (anus) which group and regroup to form different matter. A deity is the one who unites these atoms for creation and order of the universe.
Purva Mimamsa
Overview and Founder:
Jaimini established the Purva Mimamsa school that considers ritualism (karma-kanda) as an integral part of the Vedas. This school of thought highlights the essence of right conduct and duty as a means of the world’s ordination.
Core Philosophy:
Religiously sanctioned duties and the performances of rituals render spiritual merit. Mimamsa philosophy postulates that liberation (moksha) is attainable through actions (karma) disinterestedly and devotionally and in an unswerving manner.
Metaphysical Philosophy:
Vedas are placed in the highest position as infallible & eternal and are regarded as the ultimate truth comparable to a personal god. Mimamsa prefers the power of sound (shabda) and the authoritative essence of Vedic mantras.
Uttara Mimamsa / Vedanta
Overview and Founder:
Vedanta is a school of thought by Badarayana (Vyasa) which interprets the Upanishads, Bhagavad Gita, and the Brahma Sutras. It delineates the concepts of Brahman (ultimate reality) and Atman (self) and seeks to understand their relationship.
Core Philosophy:
Vedanta focuses on the objective of understanding the unity or relationship that the individual soul has with Brahman. How this relationship is interpreted, however, is different within its sub-schools.
Metaphysical View (Main Sub-Schools):
Advaita Vedanta (Shankara): Non-dualism: Brahman alone is and the world is merely an illusion. Liberation is attained by realizing that the self and Brahman are one.
Visishtadvaita Vedanta (Ramanuja): Qualified Non-dualism: Brahman (Vishnu) is a personal, loving God. Souls and matter are real parts of him. Liberation is through devotion and grace.
Dvaita Vedanta (Madhva): Dualism. God and souls are eternally distinct. The soul bliss is attained through God’s grace, but the soul will never merge with Him.
Dvaitadvaita (Nimbarka): Brahman is the ultimate reality and the master of everything.
Shuddhadvaita (Vallabhacharya): God and the individual self are one and the same.
The Heterodox Schools of Indian Philosophy (Nastika)
Unlike the six orthodox (Astika) systems, the heterodox or Nastika schools do not accept the authority of the Vedas. These schools developed independent ideas about reality, morality, and liberation, and included Carvaka, Buddhism, Jainism and Ajivika school.
Carvaka (Lokayata)
Overview and Founder:
The Carvaka or Lokayata school is the materialist philosophy of ancient India. It is traditionally attributed to Brhaspati.
Core Philosophy:
Carvaka accepts only direct perception (pratyaksha) as a valid source of knowledge and rejects all unseen or inferential reasoning. It denies the existence of the Vedas, soul, afterlife, and gods.
Metaphysical View:
According to Carvaka, only the physical world exists, consciousness arises from the body, and death is the end. The philosophy encourages people to enjoy life fully, as expressed in its well-known motto:
“Eat, drink, and be merry, for this life alone is real.”
Buddhism
Overview and Founder:
Buddhism was founded by Siddhartha Gautama (the Buddha) in the 6th century BCE. It focuses on understanding and ending human suffering through ethical living, mindfulness, and wisdom.
Core Philosophy:
Buddhism is based on the Four Noble Truths:
Life involves suffering (dukkha).
The cause of suffering is desire or attachment.
Ending desire leads to the end of suffering.
The way to end suffering is through the Eightfold Path right view, intention, speech, action, livelihood, effort, mindfulness, and concentration.
Metaphysical View:
Buddhism rejects the idea of a permanent soul (anatman) and teaches that all things are impermanent (anitya). It stresses ethical conduct, non-violence (ahimsa), and compassion (karuna). The ultimate goal is nirvana, a state of liberation and freedom from the cycle of birth and death (samsara).
Jainism
Overview and Founder:
Jainism was founded by Mahavira, a contemporary of the Buddha, in the 6th century BCE. It emphasizes self-discipline, non-violence, and truth.
Core Philosophy:
The key principles of Jainism include:
Ahimsa (non-violence): Avoiding harm to all living beings in thought, word, and deed.
Anekantavada (non-absolutism): Reality has many aspects and cannot be understood from a single viewpoint.
Syadvada (theory of conditional predication): Truth depends on perspective and context.
Liberation (moksha) is achieved by freeing the soul (jiva) from the bondage of karma through the Three Jewels (Ratnatraya) right faith, right knowledge, and right conduct.
Metaphysical View:
Jainism believes the universe is eternal and self-regulating there is no creator god. Souls are inherently pure but trapped by karma. Through austerity and self-control, one can purify the soul and attain liberation.
Ajivika School
Overview and Founder:
In the sixth century BCE, Gosala Maskariputra, a contemporary of the Buddha and Mahavira, established the Ajivika School. It reflects a unique philosophical tradition that rejects the idea that human agency shapes destiny and emphasizes fatalism.
Core Philosophy
The fundamental principles of Ajivika include:
Niyati (Fatalism): All events are predetermined; nothing occurs due to reason, cause, or individual effort. Beings become depraved or pure without inherent reason or causation.
Atman (Soul): Every being possesses an eternal soul that transmigrates but cannot be liberated through personal action, unlike other Indian philosophical schools.
Rejection of Moral Causality: Gosala Maskariputra denied the existence of sin (adharma) and rejected the concept of human freedom in determining one's fate or moral destiny.
Primary Sources:
Buddhist texts (Digha Nikaya, Anguttara Nikaya, Samyutta Nikaya) and Jaina texts (Sutrakritanga-sutra, Bhagavati-sutra, Nandi-sutra) and their commentary are the main sources of knowledge about the Ajivika school.
UPSC Previous Year Questions
Prelims
Q. “Souls are not only the property of animal and plant life, but also of rocks, running water and many other natural objects not looked on as living by other religious sects.” (2023)
The above statement reflects one of the core beliefs of which one of the following religious sects of ancient India?
Buddhism
Jainism
Shaivism
Vaishnavism
Answer: (b)
Q. Which one of the following pairs does not form part of the six systems of Indian Philosophy? (2014)
Mimamsa and Vedanta
Nyaya and Vaisheshika
Lokayata and Kapalika
Sankhya and Yoga
Answer: (c)
Q. With reference to the history of philosophical thought in India, consider the following statements regarding Sankhya school: (2013)
Sankhya does not accept the theory of rebirth or transmigration of soul.
Sankhya holds that it is the self-knowledge that leads to liberation and not any exterior influence or agent.
Which of the statements given above is /are correct?
1 only
2 only
Both 1 and 2
Neither 1 nor 2
Answer: (b)
Mains
Q. Indian Philosophy and tradition played a significant role in conceiving and shaping the monuments and their art in India. Discuss. (2020)
The six schools of Indian Philosophy (orthodox traditions) and the heterodox traditions together map the rich tapestry of Indian thought. They offer enduring insights on duty, knowledge, and liberation. Today their influence is seen in ethics, education, and public life. UPSC aspirants should know each school’s founder and main idea, and practice comparing them.
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