1. Etymology

The Sanskrit term Āstika ("pious, orthodox") refers to the systems of thought which admit the validity of the Vedas.^[1] Sanskrit asti means "there is", and Āstika (per Pāṇini 4.2.60) derives 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.^[2] 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.^[3]

Another interpretation by Swami Vivekananda states "As certain religions of the world say that a man who does not believe in a Personal God outside of himself is an atheist, so the Vedanta says, a man who does not believe in himself is an atheist. Not believing in the glory of our own soul is what the Vedanta calls atheism."^[4]

2. Historical Development

The Rig Veda, the oldest of the Vedas, deals with significant skepticism around the fundamental question of a creator God and the creation of the universe. It does not, at many instances, categorically accept the existence of a creator God. Nasadiya Sukta (Creation Hymn) in the tenth chapter of the Rig Veda states:^[5][6]

Whence was it produced? Whence is this creation?
The gods came afterwards, with the creation of this universe.

The Brihadaranyaka, Isha, Mundaka (in which Brahman is everything and "no-thing") and especially the Chandogya Upanishads have also been interpreted as atheistic because of their stress on the subjective self.^[7]

Mimamsa was a realistic, pluralistic school of philosophy which was concerned with the exegesis of the Vedas.^[8] The core text of the school was the Purva Mimamsa Sutras of Jaimini (c. 200 BCE–200 CE). Mimamsa philosophers believed that the revelation of the Vedas was sacred, authorless (apaurusheyatva) and infallible, and that it was essential to preserve the sanctity of the Vedic ritual to maintain dharma (cosmic order).^{[9][10]:52–53} As a consequence of the belief in sanctity of the ritual, Mimamsas rejected the notion of God in any form.^[8] Later commentators of the Mimamsa sutras such as Prabhākara (c. 7th century CE) advanced arguments against the existence of God.^[11][12] 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.^[13]

Samkhya is an atheistic^[14] and strongly dualistic^[15][16] orthodox (Astika) school of Indian philosophy. The earliest surviving authoritative text on classical Samkhya philosophy is the Samkhyakarika (c. 350–450 CE) of Iśvarakṛṣṇa.^[10]:63 The Samkhyakarika is silent on the issue of Isvara's existence or nonexistence, although first millennium commentators such as Gaudapada understand the text as compatible with some concept of God. However, the Samkhya Sutra (14th c. CE) and its commentaries explicitly attempt to disprove God's existence through reasoned argument.^[17]

Cārvāka, a materialistic and atheistic school of Indian philosophy, had developed a systematic philosophy by the 6th century CE. Cārvākas rejected metaphysical concepts like reincarnation, the afterlife, an extracorporeal soul, the efficacy of religious rites, other worlds (heaven and hell), fate, and accumulation of merit or demerit through the performance of certain actions. Cārvākas also refused to ascribe supernatural causes to natural phenomena. Cārvāka philosophy appears to have died out some time after 1200 CE.^[18]

Ājīvikas was a movement (extinct from at least the 13th century CE) 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.^[19]

3. Arguments Against God

Mimamsas argued that there was no need to postulate a maker for the world, just as there was no need for an author to compose the Vedas or a God to validate the rituals.^[20] They further thought that the Gods named in the Vedas had no physical existence apart from the mantras that speak their names. In this regard, the power of the mantras was what was seen as the power of Gods.^[21] Mimamsas reasoned that an incorporeal God could not author the Vedas, for he would not have the organs of speech to utter words. An embodied God could not author the Vedas either because such a God would be subject to the natural limitations of sensory knowledge and therefore, would not be able to produce supernatural revelations like the Vedas.^[22]

Samkhya gave the following arguments against the idea of an eternal, self-caused, creator God:^[23]

• If the existence of karma is assumed, the proposition of God as a moral governor of the universe is unnecessary. For, if God enforces the consequences of actions then he can do so without karma. If however, he is assumed to be within the law of karma, then karma itself would be the giver of consequences and there would be no need of a God.
• Even if karma is denied, God still cannot be the enforcer of consequences. Because the motives of an enforcer God would be either egoistic or altruistic. Now, God's motives cannot be assumed to be altruistic because an altruistic God would not create a world so full of suffering. If his motives are assumed to be egoistic, then God must be thought to have desire, as agency or authority cannot be established in the absence of desire. However, assuming that God has desire would contradict God's eternal freedom which necessitates no compulsion in actions. Moreover, desire, according to Samkhya, is an attribute of prakriti and cannot be thought to grow in God. The testimony of the Vedas, according to Samkhya, also confirms this notion.
• Despite arguments to the contrary, if God is still assumed to contain unfulfilled desires, this would cause him to suffer pain and other similar human experiences. Such a worldly God would be no better than Samkhya's notion of higher self.
• Furthermore, there is no proof of the existence of God. He is not the object of perception, there exists no general proposition that can prove him by inference and the testimony of the Vedas speak of prakriti as the origin of the world, not God.

Therefore, Samkhya maintained not only that the various cosmological, ontological and teleological arguments could not prove God, but that God as normally understood--an omnipotent, omniscient, benevolent creator who is free from suffering--cannot exist.

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:^[24]

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.

According to Markandey Katju, former Chairman of the Press Council of India and former judge of the Supreme Court of India, "...there are six classical systems of Indian philosophy, Nyaya, Vaisheshik, Sankya, Yoga, Purva Mimansa and Uttar Mimansa, and three non-classical systems, Buddhism, Jainism and Charvak. Out of these nine systems eight of them are atheistic as there is no place for God in them. Only the ninth one, that is Uttar Mimansa, which is also called Vedanta, has a place for God in it."^[25][26]

4. Notable Hindu Atheists

• Brahmananda Swami Sivayogi was an atheist and rationalist who founded the organization Ananda Mahasabha.^[27]
• Vinayak Damodar Savarkar, the president of Hindu Mahasabha, described himself as a Hindu atheist.^[28][29][30]
• Shreela Flather, Baroness Flather of Windsor and Maidenhead (1934– ), the first Hindu woman in British politics. She has described herself as a "Hindu atheist". Broadly, she is an atheist with affinity to secular aspects of Hindu culture such as dress and diet.^[31][32]