(From the Middle French athéisme, which is from the Greek atheos (αθεóς), "godless", from a-, "without" + theos, "god")

An absence of belief in the existence of gods, or the doctrine that there are no gods. This absence of belief generally comes about either through deliberate choice, or from an inherent inability to believe religious teachings which seem literally incredible. It is not a lack of belief born out of simple ignorance of religious teachings.

Some atheists go beyond a mere absence of belief in gods: they actively believe that particular gods, or all gods, do not exist. Just lacking belief in gods is often referred to as "weak atheism"; whereas believing that gods do not or cannot exist is often referred to as "strong atheism". It is important to note the difference between the strong and weak atheist positions. "Weak atheism" is simple scepticism; a lack of belief in the existence of a God. "Strong atheism" is an explicitly held belief that God does not exist. There is a qualitative difference in the "strong" and "weak" positions; it's not just a matter of degree.

Some atheists believe in the non-existence of all gods; others limit their atheism to specific gods, such as the Christian God, rather than making flat-out denials.

A popular argument against the existence of God involves the problem of evil. In 'Evil and Omnipotence', J.L. Mackie claims that the propositions "God is omnipotent", "God is wholly good", and "Evil exists" are, together, logically inconsistent and that, therefore, some important part of theistic belief is false. Other arguments resulting from this contend that the logical possibility of a wholly good God along with the horrific and extensive evil of the world is highly improbable.

Another general argument for the atheistic position argues that atheism is the proper default position: in the absence of satisfactory arguments for theism, atheism should be accepted even without satisfactory positive argument in its favor.

Compare: theism
See also: agnosticism