[Stephen]

Sorry if this contribution is short but I tend to think along the lines of 'proof' as more like 'highly probable'.

I am an atheist because, although I have no absolute proof, I believe that the probability of there being a Omnipotent, Omniscient, etc etc being is highly improbable which is good enough to convince me otherwise.

I believe in Darwin evolutionary theory because the available evidence points to a highly probable theory, without actually slam dunk complete evidence....but almost.

So FWIW, I think that using the probability yardstick allows us to avoid being stuck in either the agnostic or absolutist camps.