Atheism is, in the broadest sense, an absence of belief in the existence of deities.[1][2][3][4] Less broadly, atheism is a rejection of the belief that any deities exist.[5][6] In an even narrower sense, atheism is specifically the position that there are no deities.[1][2][7][8] Atheism is contrasted with theism,[9][10] which, in its most general form, is the belief that at least one deity exists.[10][11][12]

The etymological root for the word atheism originated before the 5th century BCE from the ancient Greek ἄθεος (atheos), meaning "without god(s)". In antiquity, it had multiple uses as a pejorative term applied to those thought to reject the gods worshiped by the larger society,[13] those who were forsaken by the gods, or those who had no commitment to belief in the gods.[14] The term denoted a social category created by orthodox religionists into which those who did not share their religious beliefs were placed.[14] The actual term atheism emerged first in the 16th century.[15] With the spread of freethought, skeptical inquiry, and subsequent increase in criticism of religion, application of the term narrowed in scope. The first individuals to identify themselves using the word atheist lived in the 18th century during the Age of Enlightenment.[16][15] The French Revolution, noted for its "unprecedented atheism," witnessed the first major political movement in history to advocate for the supremacy of human reason.[17]

Arguments for atheism range from philosophical to social and historical approaches. Rationales for not believing in deities include arguments that there is a lack of empirical evidence,[18][19] the problem of evil, the argument from inconsistent revelations, the rejection of concepts that cannot be falsified, and the argument from nonbelief.[18][20] Nonbelievers contend that atheism is a more parsimonious position than theism and that everyone is born without beliefs in deities;[1] therefore, they argue that the burden of proof lies not on the atheist to disprove the existence of gods but on the theist to provide a rationale for theism.[21] Although some atheists have adopted secular philosophies (e.g. secular humanism),[22][23] there is no one ideology or code of conduct to which all atheists adhere.[24]

Since conceptions of atheism vary, accurate estimations of current numbers of atheists are difficult.[25] According to global Win-Gallup International studies, 13% of respondents were "convinced atheists" in 2012,[26] 11% were "convinced atheists" in 2015,[27] and in 2017, 9% were "convinced atheists".[28] However, other researchers have advised caution with WIN/Gallup figures since other surveys which have used the same wording for decades and have a bigger sample size have consistently reached lower figures.[29] An older survey by the British Broadcasting Corporation (BBC) in 2004 recorded atheists as comprising 8% of the world's population.[30] Other older estimates have indicated that atheists comprise 2% of the world's population, while the irreligious add a further 12%.[31] According to these polls, Europe and East Asia are the regions with the highest rates of atheism. In 2015, 61% of people in China reported that they were atheists.[32] The figures for a 2010 Eurobarometer survey in the European Union (EU) reported that 20% of the EU population claimed not to believe in "any sort of spirit, God or life force".[33]

Definitions and types

A diagram showing the relationship between the definitions of weak/strong and implicit/explicit atheism.
Explicit strong/positive/hard atheists (in purple on the right) assert that "at least one deity exists" is a false statement.
Explicit weak/negative/soft atheists (in blue on the right) reject or eschew belief that any deities exist without actually asserting that "at least one deity exists" is a false statement.
Implicit weak/negative atheists (in blue on the left), according to authors such as George H. Smith, would include people (such as young children and some agnostics) who do not believe in a deity but have not explicitly rejected such belief.
(Sizes in the diagram are not meant to indicate relative sizes within a population.)

Writers disagree on how best to define and classify atheism,[34] contesting what supernatural entities are considered gods, whether it is a philosophic position in its own right or merely the absence of one, and whether it requires a conscious, explicit rejection. Atheism has been regarded as compatible with agnosticism,[35][36][37][38][39][40][41] but has also been contrasted with it.[42][43][44] A variety of categories have been used to distinguish the different forms of atheism.


Some of the ambiguity and controversy involved in defining atheism arises from difficulty in reaching a consensus for the definitions of words like deity and god. The variety of wildly different conceptions of God and deities leads to differing ideas regarding atheism's applicability. The ancient Romans accused Christians of being atheists for not worshiping the pagan deities. Gradually, this view fell into disfavor as theism came to be understood as encompassing belief in any divinity.[45]

With respect to the range of phenomena being rejected, atheism may counter anything from the existence of a deity, to the existence of any spiritual, supernatural, or transcendental concepts, such as those of Buddhism, Hinduism, Jainism, and Taoism.[46]

Implicit vs. explicit

Definitions of atheism also vary in the degree of consideration a person must put to the idea of gods to be considered an atheist. Atheism has sometimes been defined to include the simple absence of belief that any deities exist. This broad definition would include newborns and other people who have not been exposed to theistic ideas. As far back as 1772, Baron d'Holbach said that "All children are born Atheists; they have no idea of God."[47] Similarly, George H. Smith (1979) suggested that: "The man who is unacquainted with theism is an atheist because he does not believe in a god. This category would also include the child with the conceptual capacity to grasp the issues involved, but who is still unaware of those issues. The fact that this child does not believe in god qualifies him as an atheist."[48] Implicit atheism is "the absence of theistic belief without a conscious rejection of it" and explicit atheism is the conscious rejection of belief. For the purposes of his paper on "philosophical atheism", Ernest Nagel contested including the mere absence of theistic belief as a type of atheism.[49] Graham Oppy classifies as innocents those who never considered the question because they lack any understanding of what a god is. According to Oppy, these could be one-month-old babies, humans with severe traumatic brain injuries, or patients with advanced dementia.[50]

Positive vs. negative

Philosophers such as Antony Flew[51] and Michael Martin[45] have contrasted positive (strong/hard) atheism with negative (weak/soft) atheism. Positive atheism is the explicit affirmation that gods do not exist. Negative atheism includes all other forms of non-theism. According to this categorization, anyone who is not a theist is either a negative or a positive atheist. The terms weak and strong are relatively recent, while the terms negative and positive atheism are of older origin, having been used (in slightly different ways) in the philosophical literature[51] and in Catholic apologetics.[52] Under this demarcation of atheism, most agnostics qualify as negative atheists.

While Martin, for example, asserts that agnosticism entails negative atheism,[38] many agnostics see their view as distinct from atheism,[53][54] which they may consider no more justified than theism or requiring an equal conviction.[53] The assertion of unattainability of knowledge for or against the existence of gods is sometimes seen as an indication that atheism requires a leap of faith.[55][56] Common atheist responses to this argument include that unproven religious propositions deserve as much disbelief as all other unproven propositions,[57] and that the unprovability of a god's existence does not imply equal probability of either possibility.[58] Australian philosopher J.J.C. Smart even argues that "sometimes a person who is really an atheist may describe herself, even passionately, as an agnostic because of unreasonable generalized philosophical skepticism which would preclude us from saying that we know anything whatever, except perhaps the truths of mathematics and formal logic."[59] Consequently, some atheist authors such as Richard Dawkins prefer distinguishing theist, agnostic and atheist positions along a spectrum of theistic probability—the likelihood that each assigns to the statement "God exists".[60]

Definition as impossible or impermanent

Before the 18th century, the existence of God was so accepted in the Western world that even the possibility of true atheism was questioned. This is called theistic innatism—the notion that all people believe in God from birth; within this view was the connotation that atheists are simply in denial.[61]

There is also a position claiming that atheists are quick to believe in God in times of crisis, that atheists make deathbed conversions, or that "there are no atheists in foxholes".[62] There have, however, been examples to the contrary, among them examples of literal "atheists in foxholes".[63]

Some atheists have challenged the need for the term "atheism". In his book Letter to a Christian Nation, Sam Harris wrote:

In fact, "atheism" is a term that should not even exist. No one ever needs to identify himself as a "non-astrologer" or a "non-alchemist". We do not have words for people who doubt that Elvis is still alive or that aliens have traversed the galaxy only to molest ranchers and their cattle. Atheism is nothing more than the noises reasonable people make in the presence of unjustified religious beliefs.[64]

Pragmatic atheism

Pragmatic atheism is the view one should reject a belief in a god or gods because it is unnecessary for a pragmatic life. This view is related to apatheism and practical atheism.[65]