Romans once called Christians atheists for ignoring the pagan gods
What counts as atheism depends on what counts as a god. Ancient Romans branded Christians atheists because they refused to worship Rome's deities. Today philosophers still argue over whether atheism is a firm denial that gods exist or simply the absence of belief, a definition broad enough to include newborns.
The narrowest version holds that there are no deities; a broader one rejects belief in them; the widest just means lacking such belief. Writers disagree over which supernatural beings qualify as gods, whether atheism is a philosophical position at all, and whether it needs a conscious rejection. The usual practice is to define it as an explicit stance against theism, the belief that at least one god exists.
Philosophers have drawn finer lines. Implicit atheism means lacking theistic belief without having rejected it, while explicit atheism is a deliberate rejection. Ernest Nagel objected to counting mere absence of belief as atheism at all. Antony Flew and Michael Martin separated positive, or strong, atheism, which affirms that gods do not exist, from negative, or weak, atheism, covering every other kind of non-belief. Baron d'Holbach argued as early as 1772 that all children are born without any idea of God.
Common reasons offered for disbelief include lack of evidence, the problem of evil, conflicting revelations from different religions, the rejection of claims that cannot be falsified, and the argument from nonbelief. Atheists also push back on agnosticism, arguing that being unable to prove a god's existence does not make belief and disbelief equally likely.
The idea has deep roots in classical antiquity and early Indian philosophy. In early Greek, átheos meant godless and served as an insult for impiety; by the fifth century BCE it had come to mean actively denying the gods. In the Christian West, before the eighteenth century, belief in God was so assumed that some doubted genuine atheism was possible, imagining unbelievers were simply in denial. The English word atheist is found by 1566, earlier than atheism itself. Atheistic thought revived in Europe from the sixteenth century and through the Enlightenment.
Source: Atheism
