In the last couple days this blog has generated some discussion on the definition of “atheist” which follows from the definition of “God”. So let me offer my two cents.
First, it is crucial to keep in mind that “atheist” has always been a relative term. This is certainly true of the Greek word atheos which describes one as being “without God” (or “without a god”). Consider as an example the famous martyrdom of Polycarp, Bishop of Smyrna, c. AD 150. Polycarp was taken in front of a stadium of people and told to “renounce the atheists” by which the proconsul meant “the Christians.” Polycarp went on to oblige. He renounced the “atheists”. But his gesture cleverly revealed that he was referring to the stadium full of pagans. That bold gesture sealed his fate and he was burned at the stake.
And so it is today. Different groups can both claim the word “god” while drawing the conclusion that others who reject their understanding of God are, in fact, atheists.
This is how I can call Mormons “atheists” without a blush. (For my arguments that Mormons are atheists see here and here.) Yes, Mormons recognize a panoply of gods to rival the most god-intoxicated Hindu. But none of the entities that Mormons call gods have the core attributes with which western monotheists have identified the concept, including attributes like aseity, eternity, and some sense of immutability. What Mormons call gods are substantially like the kinds of beings the ancient Greeks recognized as gods, i.e. glorified superheros and supervillains.
Now you might be wondering, with so much disagreement about how the word God is to be used (or, to put it another way, with so many distinct concepts identified with the same word) doesn’t the word become meaningless?
No, not meaningless. Something similar is true of all sorts of other terms as well. Take “marriage” for example. Jim and Jane are married, and most people have no problem with that. But can Jack and John be married? Now watch the sparks fly. How about Sheikh Abdul and three hundred wives? Is that a legitimate matrimonial arrangement?
The proponent of Jim and Jane’s marriage might recognize that Jack and John and Sheikh Abdul and his three hundred wives all believe that they are in legitimate matrimonial relationships. But that does not mean that the proponent of Jim and Jane’s marriage is likewise obliged to recognize those other arrangements as legitimate token instances of the concept of marriage.
Likewise, the theist (Christian or otherwise) can recognize there are many other concepts of God out there, but they will not consider all of those concepts legitimate such that adherence to one of them will be sufficient to count one as a theist. In other words, one man’s theist is another man’s atheist.

