Terry Pratchett is not strictly speaking an Atheist. He is a member of the Humanist association of Britain(although Im not sure thats there official name).
He doesnt condemn the idea of there being a god so much as the human traits that we apply to them. This comes up in the Discworld novels with the horsemen of the apocalypse.
Terry seems to be firmly of the opinon (and I tend to agree) that gods are a creation of man. Without people to believe in them, a god doesn't exist. And the more people believe in a god, the stronger that god becomes.
It has always seemed to me that gods are created to explain the unexplainable. To give hope that death is not the end of existance and to try to give some sort of reason for our existance.
Surely it means not believing in any god or gods, not just God. If you believe the flying teapot is a god, how is that different to being a member of any other religion? The Christian god is not the same as others, but people who beieve in these gods aren't atheists.
an atheist believes that no god exists and therefore if they are right there is no entity of any kind.
but an agnostic may not believe in a god it does not mean they actually believ there is no god/entity.