The Greek for God was theos; when the prefix "a" was placed before it, we get the origin of "atheism," signifying a denial of the god, or gods. The word should be distinguished from "agnosticism," which means neither to affirm nor to deny but to remain in doubt; and from "infidel", which means that one does not believe some doctrine. Christians call Mohammedans "infidels" because they do not believe the Bible; Mohammendans call Christians "infidels" because they do not believe the Koran. Inasmuch as Masonry requires of a petitioner that he believe in God, the atheist is automatically excluded from the Fraternity.