In a narrower sense, atheism is specifically the position that there are no deities. Most inclusively, atheism is the absence of belief that any deities exist. Atheism is contrasted with theism, which, in its most general form, is the belief that at least one deity exists.

The term "atheism" originated from the Greek (atheos), meaning "without god(s)", used as a pejorative term applied to those thought to reject the gods worshiped by the larger society. 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. The French Revolution, noted for its "unprecedented atheism," witnessed the first major political movement in history to advocate for the supremacy of human reason.

Arguments for atheism range from the philosophical to social and historical approaches. Rationales for not believing in deities include arguments that there is a lack of empirical evidence; the problem of evil; the argument from inconsistent revelations; the rejection of concepts that cannot be falsified; and the argument from nonbelief. Although some atheists have adopted secular philosophies (eg. humanism and skepticism), there is no one ideology or set of behaviors to which all ath . . . more

https://en.wikipedia.org/wiki/Atheism