Atheism

Atheism, in the broadest sense, is an absence of belief in the existence of deities. Less broadly, atheism is a rejection of the belief that any deities exist. In an even narrower sense, atheism is specifically the position that there are no deities. Atheism is contrasted with theism, which is the belief that at least one deity exists.

Historically, evidence of atheistic viewpoints can be traced back to classical antiquity and early Indian philosophy. In the Western world, atheism declined after Christianity gained prominence. The 16th century and the Age of Enlightenment marked the resurgence of atheistic thought in Europe. Atheism achieved a significant position worldwide in the 20th century. Estimates of those who have an absence of belief in a god range from 500 million to 1.1 billion people. Atheist organizations have defended the autonomy of science, freedom of thought, secularism, and secular ethics.

Arguments for atheism range from philosophical to social approaches. Rationales for not believing in deities include the lack of evidence, the problem of evil, the argument from inconsistent revelations, the rejection of concepts that cannot be falsified, and the argument from nonbelief. Nonbelievers contend that atheism is a more parsimonious position than theism and that everyone is born without beliefs in deities; 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.

Writers disagree on how best to define and classify atheism, contesting what supernatural entities are considered gods, whether atheism is a philosophical position or merely the absence of one, and whether it requires a conscious, explicit rejection; however, the norm is to define atheism in terms of an explicit stance against theism. Atheism has been regarded as compatible with agnosticism, but has also been contrasted with it.

Some of the ambiguity involved in defining atheism arises from 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. 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. 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 been defined as the 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." Similarly, George H. Smith 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."

Implicit atheism is "the absence of theistic belief without a conscious rejection of it" and explicit atheism is the conscious rejection of belief. It is usual to define atheism in terms of an explicit stance against theism. For the purposes of his paper on "philosophical atheism", Ernest Nagel contested including the mere absence of theistic belief as a type of atheism. Graham Oppy classifies as innocents those who never considered the question because they lack any understanding of what a god is, for example one-month-old babies.

Philosophers such as Antony Flew and Michael Martin 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. Michael Martin, for example, asserts that agnosticism entails negative atheism. Agnostic atheism encompasses both atheism and agnosticism. However, many agnostics see their view as distinct from atheism.

According to atheists' arguments, unproven religious propositions deserve as much disbelief as all other unproven propositions. Atheist criticism of agnosticism says that the unprovability of a god's existence does not imply an equal probability of either possibility. Australian philosopher J.J.C. Smart 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." 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".