Atheism (Sanskrit: nir-īśvara-vāda, lit. "statement of no Lord", "doctrine of godlessness") or disbelief in God or gods has been a historically propounded viewpoint in many of the orthodox and heterodox streams of Hindu philosophies. Generally, atheism is valid in Hinduism, but the path of the atheist is viewed as very difficult to follow in matters of spirituality. 
The Sanskrit term Āstika ("pious, orthodox") refers to the systems of thought which admit the validity of the Vedas. Sanskrit asti means "there is", and Āstika (per Pāṇini 4.2.60) is derived from the verb, meaning "one who says 'asti'".
Technically, in Hindu philosophy; the term Āstika refers only to acceptance of authority of Vedas, not belief in the existence of God. However, though not accepted universally; Āstika is sometimes translated as "theist" and Nāstika as "atheist", assuming the rejection of Vedas to be synonymous to the rejection of God.
Among the six Astika schools of Hindu philosophy, the Samkhya do not accept God and the early Mimamsa also rejected the notion of God. The early Mimamsa not only did not accept God but said that human action itself was enough to create the necessary circumstances for the enjoyment of its fruits.
The atheistic viewpoint as present in the Samkhya and Mimamsa schools of Hindu philosophy takes the form of rejecting a creator-God. The Samkhya school believed in a dual existence of Prakriti ("nature") and Purusha ("spirit") and had no place for an Ishvara ("God") in its system. The early Mimamsakas believed in a adrishta ("unseen") that was the result of performing karmas ("works") and saw no need for an Ishvara in their system. Mimamsa, as a philosophy, deals exclusively with karma and thus is sometimes called Karma-Mimamsa. The karmas dealt with in Mimamsa concern the performance of Yajnas ("sacrifices to gods") enjoined in the Vedas.
Vedanta (Ved + Ant or End of Vedas) literature comprising of Upanishads and Gitas, like the later traditions of Buddha and Maha Vira emphasize self discovery through direct understanding and experience rather than any belief in god. Some interpret the word Vedanta as gist of Vedas revealed to sages at the end of Vedic period, while others consider Vedanta as end of Vedas, since Upanishads are not based on rituals and belief systems. Buddhism, Jainism and Yoga might have originated from Upanishads.
In Indian philosophy, three schools of thought are commonly referred to as nastika: Jainism, Buddhism and Cārvāka for rejecting the doctrine of Vedas. In this usage, nastika refers to the non-belief of Vedas rather than non-belief of God. However, all these schools also rejected a notion of a creationist god and so the word nastika became strongly associated with them.
Cārvāka, an atheistic school of Indian philosophy, traces its origins to 600 BCE, while some claim earlier references to such positions. It was a hedonistic school of thought, advocating that there is no afterlife. Cārvāka philosophy appears to have died out some time after 1400 CE.
Dharmakirti, a 7th century buddhist philosopher deeply influenced by cārvāka philosophy, wrote in Pramanvartik:
वेद प्रामाण्यं कस्य चित् कर्तृवादः स्नाने धर्मेच्छा जातिवादाव लेपः|
संतापारंभः पापहानाय चेति ध्वस्तप्रज्ञानां पञ्च लिङगानि जाड्ये||
Believing that the Veda are standard (holy or divine), believing in a Creator for the world,
Bathing in holy waters for gaining punya, having pride (vanity) about one's caste,
Performing penance to absolve sins,
Are the five symptoms of having lost one's sanity.
Buddhism and Jainism have their origins in pre-historic sramana tradition and are not hedonistic. Also worth mentioning are the Ājīvikas (now an extinct religion), whose founder, Makkhali Gosala, was a contemporary of Mahavira and Gautama Buddha (the central figures of Jainism and Buddhism, respectively). Gosala and his followers also denied the existence of a creator god.
Hindu atheists in recent times
The Indian Nobel Prize-winner Amartya Sen, in an interview with Pranab Bardhan for the California Magazine published in the July-August 2006 edition by the University of California, Berkeley states:
|“||In some ways people had got used to the idea that India was spiritual and religion-oriented. That gave a leg up to the religious interpretation of India, despite the fact that Sanskrit had a larger atheistic literature than what exists in any other classical language. Madhava Acharya, the remarkable 14th century philosopher, wrote this rather great book called Sarvadarshansamgraha, which discussed all the religious schools of thought within the Hindu structure. The first chapter is "Atheism" - a very strong presentation of the argument in favor of atheism and materialism.||”|
- Amartya Sen, Economist and 1998 Nobel laureate.
- Vinayak Damodar Savarkar, the president of Hindu Mahasabha, described himself as a Hindu atheist. He is credited for developing a Hindu nationalist political ideology he termed as Hindutva ("Hinduness").
- Shreela Flather, Baroness Flather of Windsor and Maidenhead, the first Hindu woman in British politics. She described herself as a "Hindu atheist". Broadly, she is an atheist with affinity to secular aspects of Hindu culture such as dress and diet.
- Periyar - Founder of the Dravidian social activist
- Amol Palekar - a notable Hindi and Marathi Filmmaker, openly claims to be agnostic and atheist, even though brought up in a Hindu background.
- Vijay Tendulkar - a famous Marathi writer and dramatist who was also known to be an atheist.
- G. A. Kulkarni - a Sahitya Akademi Award winner Marathi writer has expressed his atheist views through his correspondence with other famous literary figures like Sunitabai Deshpande, Jaywant Dalvi, Shri.Na. Pendse, et al. + *Periyar - Founder of the Dravidian social activist
- Manabendra Nath Roy, Bengali Indian revolutionary, political theorist and activist, founder of the Communist parties in Mexico and India.
- Dr. Shriram Lagoo, notable Marathi actor and rationalist activist.
- A. N. Murthy Rao - Prominent Kannada writer who wrote acclaimed book Devaru (God) rejecting the concept of god.
- K. Shivaram Karanth - Jnanapita award winner. He reflects his beliefs in his novel Mookajjiya Kanasugalu.
- Prabir Ghosh - The General Secretaty of The Science and Rationalists' Association of India
- Narendra Nayak - Founder of Dakshina Kannada Rationalist Association.
- M.Karunanidhi - Tamil Nadu chief minister
- Atheism in India
- Ajita Kesakambali
- The Speak Tree - The Atheistic Roots of Hindu Philosophy. The Times of India.
- Atheism in Hinduism
- Chakravarti, Sitansu (1991). Hinduism, a way of life. Motilal Banarsidass Publ.. p. 71. ISBN 9788120808997. http://books.google.co.in/books?id=J_-rASTgw8wC&pg=PA71.
- Verma, Rajeev (2009). Faith & philosophy of Hinduism - Volume 1 of Indian religions series. Gyan Publishing House. p. 10. ISBN 9788178357188. http://books.google.co.in/books?id=J7AIg5bVFCYC&pg=PA10.
- Pruthi (2004). Vedic civilization - Culture and civilization series. Discovery Publishing House. p. 214. ISBN 9788171418756. http://books.google.co.in/books?id=z3ksBrWoZm0C&pg=PA214.
- Kapoor, Subodh. The Systems of Indian Philosophy. Genesis Publishing Pvt Ltd. p. 6. ISBN 9788177558876. http://books.google.co.in/books?id=FWLRyXBzgsoC&pg=PA6.
- Monier-Williams (1899)
- Dasgupta, Surendranath (1992). A history of Indian philosophy, Volume 1. Motilal Banarsidass Publ.. p. 258. ISBN 9788120804128. http://books.google.co.in/books?id=PoaMFmS1_lEC&pg=PA258.
- Tripathi (2001). Psycho-Religious Studies of Man, Mind and Nature. Global Vision Publishing House. p. 81. ISBN 9788187746041. http://books.google.co.in/books?id=zWFM_SaX24AC&pg=PA81.
- History and Doctrines of the Ājīvikas: A Vanished Indian Religion
- Athavale, Sadashiv. Charvak Itihas ani Tatvadynan (III ed ed.). p. 24.
- Balsham, B.L. (2003). History and Doctrines of the Ājīvikas: A Vanished Indian Religion. Motilal Banarsidass Publ. ISBN 8120812042. http://www.google.com/books?id=BiGQzc5lRGYC&.
- California Magazine
- Reported lecture facinghistory.org
- Self-proclaimed chowk.com
- World Bank worldbank.org
- Press meeting rediff.com
- Kumar, Pramod (1992). Towards Understanding Communalism. Chandigarh: Centre for Research in Rural and Industrial Development. p. 348. ISBN 9788185835174. OCLC 27810012. "VD Savarkar was publicly an atheist.Even when he was the Hindu Mahasabha leader he used to publicly announce and advertise lectures on atheism, on why god is not there and why all religions are false. That is why when defining Hindutva, he said, Hindutva is not defined by religion and tried to define it in a non-religious term: Punyabhoomi."
- Nandy, Ashis (2003). Time Warps: The Insistent Politics of Silent and Evasive Pasts. Delhi: Orient Longman. p. 71. ISBN 9788178240718. OCLC 49616949.
- BBC News
- G.A.-chi Nivadak Patre: Khand 1 & 2 (Selected Letters of G.A. : Part 1 & 2), Mauj Prakashan
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