'?stika derives from the Sanskrit asti, "there is, there exists", and means "one who believes in the existence (of God, of another world, &c.)" and n?stika means "an atheist or unbeliever" . These have been concepts used to classify Indian philosophies by modern scholars, and some Hindu, Buddhist and Jaina texts.?stika has been defined in one of three ways; as those who accept the epistemic authority of the Vedas, as those who accept the existence of ?tman, or as those who accept the existence of Ishvara. In contrast, n?stika are those who deny the respective definitions of ?stika.
The various definitions for ?stika and n?stika philosophies has been disputed since ancient times, and there is no consensus.Buddhism is considered to be n?stika, but the Gautama Buddha is considered an avatar of Vishnu in some Hindu traditions. The most studied ?stika schools of Indian philosophies, sometimes referred to as orthodox schools, are six: Ny?yá, Vai?e?ika, Skhya, Yoga, M?ms?, and Ved?nta - all schools of Hinduism. The most studied N?stika schools of Indian philosophies, sometimes referred to as heterodox schools, are four: Buddhism, Jainism, C?rv?ka, and ?j?vika - last two are also schools of Hinduism. This orthodox-heterodox terminology is a construct of Western languages, and lacks scholarly roots in Sanskrit. Recent scholarly studies state that there have been various heresiological translations of ?stika and N?stika in 20th century literature on Indian philosophies, but quite many are unsophisticated and flawed.
Astika and N?stika do not mean "theism" and "atheism" respectively in ancient or medieval era Sanskrit literature. In current Indian languages like Hindi, ?stika and its derivatives usually mean "theist", while n?stika and its derivatives denote an "atheist." However, the terms are used differently in Hindu philosophy. For example, Skhya is both an atheist and ?stika (Vedic) philosophy.
As used in Hindu philosophy the differentiation between ?stika and n?stika does not refer to theism or atheism. The terms often, but not always, relate to accepting Vedic literature as an authority, particularly on their teachings on Self (Soul). The Veda and Hinduism do not subscribe to or include the concept of an almighty that is separate from oneself i.e. there is no concept of 'god' as in the Christian or Islamic sense. As N. N. Bhattacharyya writes:
The followers of Tantra were often branded as N?stika by the political proponents of the Vedic tradition. The term N?stika does not denote an atheist since the Veda presents a godless system with no singular almighty being or multiple almighty beings. It is applied only to those who do not believe in the Vedas. The Skhyas and M?msakas do not believe in God, but they believe in the Vedas and hence they are not N?stikas. The Buddhists, Jains, and C?rv?kas do not believe in the Vedas; hence they are N?stikas.-- N. N. Bhattacharyya
The terms ?stika and N?stika have been used to classify various Indian intellectual traditions.
A list of six systems or ?a?dar?anas (also spelled Sad Darshan) consider Vedas as a reliable source of knowledge and an authoritative source. These are the Nyaya, Vaisheshika, Samkhya, Yoga, Mims? and Vedanta schools of Hinduism, and they are classified as the ?stika schools:
These are often coupled into three groups for both historical and conceptual reasons: Ny?yá-Vai?e?ika, Skhya-Yoga, and Mims?-Vedanta.
The use of the term n?stika to describe Buddhism and Jainism in India is explained by Gavin Flood as follows:
At an early period, during the formation of the Upani?ads and the rise of Buddhism and Jainism, we must envisage a common heritage of meditation and mental discipline practiced by renouncers with varying affiliations to non-orthodox (Veda-rejecting) and orthodox (Veda-accepting) traditions.... These schools [such as Buddhism and Jainism] are understandably regarded as heterodox (n?stika) by orthodox (?stika) Brahmanism.-- Gavin Flood
Tantric traditions in Hinduism have both ?stika and n?stika lines; as Banerji writes in "Tantra in Bengal":
Tantras are ... also divided as ?stika or Vedic and n?stika or non-Vedic. In accordance with the predominance of the deity the ?stika works are again divided as kta, ?aiva, Saura, Gapatya and Vaiava.-- Banerji
Manusmriti, in verse 2.11, defines N?stika as those who revile "Vedic literature based on two roots of science of reasoning (?ruti and Smriti)". The 9th century Indian scholar Medhatithi analyzed this definition and stated that N?stika does not mean someone who says "Vedic literature are untrue", but rather one who says "Vedic literature are immoral". Medhatithi further noted verse 8.309 of Manusmriti, to provide another aspect of the definition of N?stika as one who believes, "there is no other world, there is no purpose in giving charity, there is no purpose in rituals and the teachings in the Vedic literature."
Manusmriti does not define, or imply a definition for Astika. It is also silent or contradictory on specific rituals such as animal sacrifices, asserting Ahimsa (non-violence, non-injury) is dharma in its verses such as verse 10.63 based on Upanishadic layer of Vedic literature, even though the older layer of Vedic literature mention such sacrifices unlike the later layer of Vedic literature. Indian scholars, such as those from Samkhya, Yoga, Nyaya and Vedanta schools, accepted Astika to be those that include ?abda (?, Aptavacana, testimony of Vedic literature and reliable experts) as a reliable means of epistemology, but they accepted the later ancient layer of the Vedic literature to be superseding the earlier ancient layer.
In contrast to Manusmiriti, the 6th century CE Jain scholar and doxographer Haribhadra, provided a different perspective in his writings on Astika and N?stika. Haribhadra did not consider "reverence for Vedas" as a marker for an Astika. He and other 1st millennium CE Jaina scholars defined Astika as one who "affirms there exists another world, transmigration exists, virtue (punya) exists, vice (paap) exists".
The 7th century scholars Jayaditya and Vamana, in Kasikavrtti of Panini tradition, were silent on the role of or authority of Vedic literature in defining Astika and N?stika. They state, "Astika is the one who believes there exists another world. The opposite of him is the N?stika."
Similarly the widely studied 2nd-3rd century CE Buddhist philosopher Nagarjuna, in Chapter 1 verses 60-61 of Ratn?val?, wrote Vai?e?ika and Skhya schools of Hinduism were N?stika, along with Jainism, his own school of Buddhism and Pudgalavadins (V?ts?putr?ya) school of Buddhism.
Astika, in some texts, is defined as those who believe in the existence of Atman (Soul, Self, Spirit), while Nastika being those who deny there is any "soul, self" in human beings and other living beings. All six schools of Hinduism classified as Astika philosophies hold the premise, "Atman exists". Buddhism, in contrast, holds the premise, "Atman does not exist". Asanga Tilakaratna translates Astika as "positivism" and Nastika as "negativism", with Astika illustrated by Brahmanic traditions who accepted "soul and God exists", while Nastika as those traditions, such as Buddhism, who denied "soul and God exists".
According to G. S. Ghurye, the Jain texts define "na+astika" as one "denying what exists" or any school of philosophy that denies the existence of the soul. The Vedanta sub-traditions of Hinduism are "astika" because they accept the existence of soul, while Buddhist traditions denying this are referred to as "nastika".
One of the earliest mentions of astika concept in Jain texts is by Manibhadra, who states that an astika is one who "accepts there exist another world (paraloka), transmigration of soul, virtue and vice that affect how a soul journeys through time".
The 5th-6th century Jainism scholar Haribhadra, states Andrew Nicholson, does not mention anything about accepting or rejecting the Vedas or god as a criterion for being an astika or nastika. Instead, Haribhadra explains nastika in the manner of the more ancient Jain scholar Manibhadra, by stating a nastika to be one "who says there is no other worlds, there is no purpose in charity, there is no purpose in offerings". An astika, to Haribhadra, is one who believes that there is a purpose and merit in an ethical life such as ahimsa (non-violence) and ritual actions. This exposition of the word astika and nastika by Haribhadra is similar to one by the Sanskrit grammarian and Hindu scholar Panini in section 4.4.60 of the Astadhyayi.
The 4th century Buddhist scholar Asanga, in Bodhisattva Bhumi, calls nastika Buddhists as sarvavai nasika, describing them as who are complete deniers. To Asanga, nastika are those who say "nothing whatsoever exists", and the worst kind of nastika are those who deny all designation and reality. Astika are those who accept merit in and practice a religious life. According to Andrew Nicholson, later Buddhists understood Asanga to be targeting Madhyamaka Buddhism as nastika, while considering his own Yogacara Buddhist tradition to be astika. Initial interpretations of the Buddhist texts with the term astika and nastika, such as those composed by Nagarjuna and Asvaghosa, were interpreted as being directed at the Hindu traditions. But, states John Kelly, most later scholarship considers this as incorrect, and that the astika and nastika terms were directed towards the competing Buddhist traditions and the intended audience of the texts were Buddhist monks debating an array of ideas across various Buddhist traditions.
The charges of being a nastika were serious threat to the social standing of a Buddhist, and could lead to expulsion from Buddhist monastic community. Thus, states Nicholson, the colonial era Indologist definition of astika and nastika schools of Indian philosophy, was based on a narrow study of literature such as a version of Manusmriti, while in truth these terms are more complex and contextually apply within the diverse schools of Indian philosophies.
The most common meaning of astika and nastika, in Buddhism, Hinduism and Jainism was the acceptance and adherence to ethical premises, and not textual validity or doctrinal premises, states Nicholson. It is likely that astika was translated as orthodox, and nastika as heterodox, because the early European Indologists carried the baggage of Christian theological traditions and extrapolated their own concepts to Asia, thereby distorting the complexity of Indian traditions and thought.
In modern Indian languages, "?stika" and "n?stika" generally mean "theist" and "atheist," respectively. But in Sanskrit philosophical literature, "?stika" means "one who believes in the authority of the Vedas". ("n?stika" means the opposite of these). The word is used here in the first sense. The six orthodox schools are "?stika", and the C?rv?ka is "n?stika" in both the senses.