You raise a good point and I know where you are coming from because I
held the same position less than 2 years ago. I've since come to realize
that atheists can consistently believe that god does not exist, but it
really depends on semantics.
In "Atheism: a philosophical justification", Michael Martin makes a
distinction between negative atheists (those who don't believe in God)
and positive atheists (those who believe God does not exist). The first
half of this 600 page book is devoted to showing that negative atheism
is a rational position by refuting arguments for the existence of God.
The 2nd half shows that positive atheism is also a rational position
by advancing many arguments for the non-existence of God. For example,
Martin shows (and I tend to agree) that God can't exist because the
concept of an omniscient, omnipotent, perfectly moral being is incoherent
and therefore logically impossible. Several other arguments were offered
in the form of "if God exists then X would be true. Since X is not true,
God does not exist". These types of arguments don't preclude the possibility
that God exists completely independent of human civilization, but that
also precludes most people's conception of God.
If that isn't enough justification, there is also the fact that beliefs
are not theorems to be proved or disproved, they are provisional assumptions
based on the best available evidence. But that is another tread.
I welcome your comments,
-- David McFadzean dbm@merak.com Memetic Engineer http://www.merak.com/~dbm/ Merak Projects Ltd.