The spontaneous proposition that there may be no gods after all is likely as old as theism itself (and the proposition that there may be no God as old as the beginnings of monotheism or henotheism). Philosophical atheist thought appears from the 6th or 5th century BCE, both in Europe and in Asia.
Although these religions claim to offer a philosophic and salvific path not centering on deity worship, popular tradition in some sects of these religions has long embraced deity worship, the propitiation of spirits, and other elements of folk tradition. Furthermore, the Pali Tripiṭaka, the oldest complete composition of scriptures, seems to accept as real the concepts of divine beings, the Vedic (and other) gods, rebirth, and heaven and hell. While deities are not seen as necessary to the salvific goal of the early Buddhist tradition, their reality is not questioned.
The principal text of the Samkhya school, the Samkhya Karika, was written by Ishvara Krishna in the 4th century CE, by which time it was already a dominant Hindu school. The origins of the school are much older and are lost in legend. The school was both dualistic and atheistic. They believed in a dual existence of Prakriti ("nature") and Purusha ("spirit") and had no place for an Ishvara ("God") in its system, arguing that the existence of Ishvara cannot be proved and hence cannot be admitted to exist. The school dominated Hindu philosophy in its day, but declined after the 10th century, although commentaries were still being written as late as the 16th century.
The foundational text for the Mimamsa school is the Purva Mimamsa Sutras of Jaimini (c. 3rd to 1st century BCE). The school reached its height c. 700 CE, and for some time in the Early Middle Ages exerted near-dominant influence on learned Hindu thought. The Mimamsa school saw their primary enquiry was into the nature of dharma based on close interpretation of the Vedas. Its core tenets were ritualism (orthopraxy), anti-asceticism and anti-mysticism. The early Mimamsakas believed in an adrishta ("unseen") that is the result of performing karmas ("works") and saw no need for an Ishvara ("God") in their system. Mimamsa persists in some subschools of Hinduism today.
In western Classical Antiquity, theism was the fundamental belief that supported the divine right of the State (Polis, later the Roman Empire). Historically, any person who did not believe in any deity supported by the State was fair game to accusations of atheism, a capital crime.
Diagoras of Melos (5th century BCE) is known as the "first atheist". He blasphemed by making public the Eleusinian Mysteries and discouraging people from being initiated. Around the same time the Atomists Leucippus and Democritus attempted to explain the world in a purely materialistic way, without reference to the spiritual or mystical.
Among the Sophists, Prodicus of Ceos was said to have believed that "it was the things which were serviceable to human life that had been regarded as gods, and Protagoras was, according to Cicero, said to have stated at the beginning of a book that "With regard to the gods I am unable to say either that they exist or do not exist.
For political reasons, Socrates in Athens (399 BCE) was accused of being 'atheos' ("refusing to acknowledge the gods recognized by the state"). Despite the charges, he claimed inspiration from a divine voice (Daimon). His dying wish that a rooster be sacrificed to the god Asclepius is unrelated to polytheistic piety: the gesture was customary for someone who had overcome an illness, and Socrates intended to convey that by dying, he had overcome the "illness" of being alive. Christians in Rome were also considered subversive to the state religion and prosecuted as atheists. Thus, charges of atheism, meaning the subversion of religion, were often used similarly to charges of heresy and impiety — as a political tool to eliminate enemies.
Euhemerus (c. 330–260 BCE) published his view that the gods were only the deified rulers, conquerors and founders of the past, and that their cults and religions were in essence the continuation of vanished kingdoms and earlier political structures. Although Euhemerus was later criticized for having "spread atheism over the whole inhabited earth by obliterating the gods", his worldview was not atheist in a strict and theoretical sense, because he differentiated that the primordial gods were "eternal and imperishable". Some historians have argued that he merely aimed at reinventing the old religions in the light of the beginning deification of political rulers such as Alexander the Great. Euhemerus' work was translated into Latin by Ennius, possibly to mythographically pave the way for the planned divinization of Scipio Africanus in Rome.
Also important in the history of atheism was Epicurus (c. 300 BCE). Drawing on the ideas of Democritus and the Atomists, he espoused a materialistic philosophy whereby the universe was governed by the laws of chance without the need for divine intervention. Although he stated that the gods existed, he believed that they were uninterested in human existence. The aim of the Epicureans was to attain peace of mind by exposing fear of divine wrath as irrational. One of the most eloquent expression of Epicurean thought is Lucretius' On the Nature of Things (1st century BCE). Lucretius was not an atheist as he did believe in the existence of gods, but like Epicurus, he thought of them as perfect beings uninterested in human affairs. Both of them also denied the existence of an afterlife. Perhaps they are better described as materialists than atheists. Epicureans were not persecuted, but their teachings were controversial, and were harshly attacked by the mainstream schools of Stoicism and Neoplatonism. The movement remained marginal, and gradually died out at the end of the Roman Empire, until it was revived by Pierre Gassendi in the 17th century.
It is remarkable that Old Norse legend occasionally mentions certain men who, turning away in utter disgust and doubt from the heathen faith, placed their reliance on their own strength and virtue. Thus in the Sôlar lioð 17 we read of Vêbogi and Râdey â sik þau trûðu, "in themselves they trusted",citing several other examples, including two kings.
In Christian Europe, people were persecuted for heresy, especially in countries where the Inquisition was active. Thomas Aquinas' five proofs for God's existence, and Anselm's ontological argument at least acknowledged the validity of the question about god's existence. The charge of atheism was used as way of attacking one's political or religious enemies. Pope Boniface VIII, because he insisted on the political supremacy of the church, was accused by his enemies after his death of holding (unlikely) atheistic positions such as "neither believing in the immortality nor incorruptibility of the soul, nor in a life to come.
In medieval Islam, scholars recognized the idea of atheism, and frequently attacked unbelievers, although they were unable to name any actual atheists; when individuals were accused of atheism, they were usually heretics rather than proponents of atheism. One notable figure was the 9th century scholar Ibn al-Rawandi who criticized the notion of religious prophecy including that of Muhammad, and maintained that religious dogmas were not acceptable to reason and must be rejected. Other critics of religion in the Islamic world include the physician and philosopher Abu Bakr al-Razi (865-925), and the poet Al-Ma`arri (973-1057).
The term athéisme itself was coined in France in the 16th century. The concept of atheism re-emerged initially as a reaction to the intellectual and religious turmoil of the Age of Enlightenment and the Reformation — as a charge used by those who saw the denial of god and godlessness in the controversial positions being put forward by others. During the 16th and 17th centuries, the word 'atheist' was used exclusively as an insult; nobody wanted to be regarded as an atheist. How dangerous it was to be accused of being an atheist at this time is illustrated by the fact that in 1689 the Polish nobleman Kazimierz Łyszczyński, who had directly denied the existence of God in his philosophical treatise De non existentia Dei, was condemned to death in Warsaw for atheism and beheaded after his tongue was pulled out with a burning iron and his hands slowly burned. Similarly in 1766, the French nobleman Jean-François de la Barre, was tortured, beheaded, and his body burned for alleged vandalism of a crucifix, a case that became celebrated because Voltaire tried unsuccessfully to have the sentence reversed.
Among those accused of atheism was Denis Diderot (1713–1784), one of the Enlightenment's most prominent philosophes, and editor-in-chief of the Encyclopédie, which sought to challenge religious, particularly Catholic, dogma: "Reason is to the estimation of the philosophe what grace is to the Christian", he wrote. "Grace determines the Christian's action; reason the philosophe's". Diderot was briefly imprisoned for his writing, some of which was banned and burned.
The English materialist philosopher Thomas Hobbes (1588–1679) was also accused of atheism, but he denied it. His theism was unusual, in that he held god to be material. Even earlier, the British playwright and poet, Christopher Marlowe (1563–1593), was accused of atheism when a tract denying the divinity of Christ was found in his home. Before he could finish defending himself against the charge, Marlowe was murdered, although this was not related to the religious issue.
By the 1770s, atheism was ceasing to be a dangerous accusation that required denial, and was evolving into a position openly avowed by some. The first open denial of the existence of god and avowal of atheism since classical times may be that of Paul Baron d'Holbach (1723–1789) in his 1770 work, The System of Nature. D'Holbach was a Parisian social figure who conducted a famous salon widely attended by many intellectual notables of the day, including Denis Diderot, Jean Jacques Rousseau, David Hume, Adam Smith, and Benjamin Franklin. Nevertheless, his book was published under a pseudonym, and was banned and publicly burned by the Executioner.
The pamphlet Answer to Dr Priestley's Letters to a Philosophical Unbeliever (1782) is considered to be the first published declaration of atheism in Britain — plausibly the first in English (as distinct from covert or cryptically atheist works). The otherwise unknown 'William Hammon' (possibly a pseudonym) signed the preface and postscript as editor of the work, and the anonymous main text is attributed to Matthew Turner (d. 1788?), a Liverpool physician who may have known Priestley. Historian of atheism David Berman has argued strongly for Turner's authorship, but also suggested that there may have been two authors (see Berman 1988, Chapter 5).
The freethinker Charles Bradlaugh (1833–1891) was repeatedly elected to the British Parliament, but was not allowed to take his seat after his request to affirm rather than take the religious oath was turned down (he offered to take the oath, but this too was denied him). After Bradlaugh was re-elected for the fourth time, a new Speaker allowed Bradlaugh to take the oath and permitted no objections: he became the first outspoken atheist to sit in Parliament, where he participated in amending the Oaths Act. In many countries, denying god was included as a crime of blasphemy. In several countries, such as Germany, Spain, and the United Kingdom, these laws remain , however these laws would be in direct conflict with Article 10 of the European Convention on Human Rights thus making them unenforcable relics. Likewise, some American states, such as Massachusetts, retain such laws; however, these laws are rarely enforced, if at all.
Marx believed that people turn to religion in order to dull the pain caused by the reality of social situations; that is, Marx suggests religion is an attempt at transcending the material state of affairs in a society — the pain of class oppression — by effectively creating a dream world, rendering the religious believer amenable to social control and exploitation in this world while they hope for relief and justice in life after death. In the same essay, Marx states, "...[m]an creates religion, religion does not create man..."
Friedrich Nietzsche, a prominent 19th century philosopher, is well-known for coining the aphorism "God is dead" (German: "Gott ist tot"); incidentally the phrase was not spoken by Nietzsche directly, but was used as a dialogue for the characters in his works. Nietzsche argued that Christian theism as a belief system had been a moral foundation of the Western world, and that the rejection and collapse of this foundation as a result of modern thinking (the death of God) would naturally cause a rise in nihilism or the lack of values. While Nietzsche was staunchly atheistic, he was also concerned about the negative effects of nihilism on humanity. As such, he called for a re-evaluation of old values and a creation of new ones, hoping that in doing so man would achieve a higher state he labeled the Overman.
A. J. Ayer asserted the unverifiability and meaninglessness of religious statements, citing his adherence to the empirical sciences. The structuralism of Lévi-Strauss sourced religious language to the human subconscious, denying its transcendental meaning. J. N. Findlay and J. J. C. Smart argued that the existence of God is not logically necessary. Naturalists and materialists such as John Dewey considered the natural world to be the basis of everything, denying the existence of God or immortality.
The 20th century also saw the political advancement of atheism, spurred on by interpretation of the works of Marx and Engels. State support of atheism and opposition to organized religion was made policy in all communist states, including the People's Republic of China and the former Soviet Union. In theory and in practice these states were secular. The justifications given for the social and political sidelining of religious organizations addressed, on one hand, the "irrationality" of religious belief, and on the other the "parasitical" nature of the relationship between the church and the population. Churches were sometimes tolerated, but subject to strict control - church officials had to be vetted by the state, while attendance of church functions could endanger one's career. Very often, the state's opposition to religion took more violent forms; Aleksandr Solzhenitsyn documents widespread persecution, imprisonments and torture of believers, in his seminal work The Gulag Archipelago. Consequently, religious organizations, such as the Catholic Church, were among the most stringent opponents of communist regimes. In some cases, the initial strict measures of control and opposition to religious activity were gradually relaxed in communist states. On the other hand, Albania under Enver Hoxha became, in 1967, the first (and to date only) formally declared atheist state. Hoxha went far beyond what most other countries had attempted and completely prohibited religious observance, systematically repressing and persecuting adherents. The right to religious practice was restored in 1991.
In India, E. V. Ramasami Naicker (Periyar), a prominent atheist leader, fought against Hinduism and the Brahmins for discriminating and dividing people in the name of caste and religion. This was highlighted in 1956 when he made the Hindu god Rama wear a garland made of slippers and made antitheistic statements.
During the Cold War, the United States often characterized its opponents as "Godless Communists, which tended to reinforce the view that atheists were unreliable and unpatriotic. Against this background, the words "under God" were inserted into the pledge of allegiance in 1954, and the national motto was changed from E Pluribus Unum to In God We Trust in 1956.