Recent scholarly studies state that there have been various heresiological translations of Āstika and Nāstika in 20th century literature on Indian philosophies, but many are unsophisticated and flawed.
The Buddhists, Jains, and Cārvākas do not believe in the Vedas; hence they are Nāstikas.Āstika is also a name, such as that of a Vedic scholar born to the goddess Mānasā ('Mind') and the sage Jaratkaru.
The main schools of Indian philosophy that reject the Vedas were regarded as heterodox in the tradition:[3] The use of the term nāstika to describe Buddhism and Jainism in India is explained by Gavin Flood as follows: At an early period, during the formation of the Upaniṣads 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....
In accordance with the predominance of the deity the āstika works are again divided as Śākta, Śaiva, Saura, Gāṇapatya and Vaiṣṇava.Manusmriti, in verse 2.11, defines Nāstika as those who do not accept "Vedic literature in entirety based on two roots of science of reasoning (Śruti and Smriti)".
[24] Indian scholars, such as those from Samkhya, Yoga, Nyaya and Vedanta schools, accepted Astika to be those that include Śabda (शब्द; or 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.
[5] In contrast to Manusmriti, the 6th century CE Jain scholar and doxographer Haribhadra, provided a different perspective in his writings on Astika and Nāstika.
"[5][6] The 7th century scholars Jayaditya and Vamana, in Kasikavrtti of Pāṇini tradition, were silent on the role of or authority of Vedic literature in defining Astika and Nāstika.
[32] The Vedanta sub-traditions of Hinduism are "astika" because they accept the existence of Self, while Buddhist traditions denying this are referred to as "nastika".
[33] 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.
[33] 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.
[33] This exposition of the word astika and nastika by Haribhadra is similar to one by the Sanskrit grammarian and Hindu scholar Pāṇini in section 4.4.60 of the Astadhyayi.
[34] The 12th century Jaina scholar Hemachandra similarly states, in his text Abithana Chintamani, that a nastika is any philosophy that presumes or argues there is "no virtue and vice.
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.