Atheism is, almost by definition, not an organization; its defining characteristic – lack of belief in any God or gods – rests on a principle of questioning dogmatism and authority. Although atheists do organize, such organization is generally quite informal.
Differences from Organized Religion
It is erroneous to speak of atheism as a centralized group, much less a religion.
Although there are national atheist groups with local chapters, these are not officially representative of "atheism" in the same way that e.g. Catholic bishops officially represent the Catholic Church – there is no official organization which defines the beliefs and membership of "atheism" the way the Catholic Church can confirm or excommunicate its members into or out of Catholicism, whose definition is also completely controlled by the Church's central authority. "Atheism" is an expression of a principle which rejects the very idea of dogma and tends to be very leery of doctrine.
Atheism is a simple idea, a word meaning "disbelief in God(s)", and individuals who agree with that idea to any extent may decide for themselves whether or not they are "atheists".
Indeed, it is almost exactly the opposite of a religion, except that there is nothing in the idea of atheism which would prevent an atheist from attending a church saying prayers, observing rituals, or displaying any of the other countless hallmarks of religion. An atheist simply wouldn't take the words as literal truth, wherever those words presumed the existence of a deity. Atheism corresponds to religious belief in much the same way that anarchism does to government.
- list of atheist organizations