Atheists believe that Gd does not exist. Most atheists believe that it is impossible to advance respectable knowledge claims in support of the belief that Gd exists, and that this purported impossibility supports their atheism.
In fact, belief that G*d does not exist requires precisely the same type of faith as does theism, namely, a belief for which it is impossible to advance respectable knowledge claims.
Most atheists will point to the fossil record, or will raise theological objections to theism, such as for example the problem of evil (if G*d exists and is all loving, then why does “he” allow suffering?).
However compelling such evidence or arguments may be, for atheists, nonetheless they supply only empirical evidence or theological arguments.
Gd by definition, at least the Gd of Jews, Christians, and Muslims, for starters, exists outside of this universe and so is, in principle, unobservable. Now, given the latest findings in quantum physics, and allowing for quibbles and concocted cases, I’m sure that what I’ve said is disbutable, however the nature of such disputes will serve to underscore the ease of comprehensibility and the general good sense of what I’m saying. Please bear in mind that this is a brief chat board posting, not a treatise.
At the end of the day atheists try to distinguish their non-empirical faith by appeals to probability, parsimony, and other scientific standards, however all such appeals serve to conceal the circularity and emptiness of empirically based arguments that G*d definitely doesn’t exist.
So far, the best accounts of the origin of the universe trail off into “something happened”. As great as the appetite of atheists may be to close the file, it remains open. Some varieties of theological doctrine can be and have been discredited. That, however, is doctrinal repudiation, not proof that G*d does not exist.
Atheists in general would like to advance their religion (I call it a religion, taking perhaps polemical license), claiming the same intellectual legitimacy that underpins Agnosticism. Empirically grounded scepticism however cannot drive a compelling case for a knowledge claim that G*d does not exist. And the rest is just more theology.
There’s a reason why “theism” appears in “atheism” – atheism is a theistic belief.