Understanding Atheism
Theism and atheism address belief in a god. Gnosticism and agnosticism address knowledge of god. Atheism means without theism. If you're not a theist, you're atheist, however agnostic or weak an atheist you may be. It is not a belief system, it does not have a doctrine, a dogma, rules, a philosophy, or anything else. Atheism does not make any claims, it is not a belief that there isn't or cannot be a god, however individual atheists may hold that view. Atheism is simply the passive rejection of the theistic claim that there is a god. It is a default position until one becomes convinced of the existence of a god.
Athiests hold varying views just as believers do. Some atheists believe in an afterlife, some in reincarnation. Some atheists believe in the paranormal, some are even mystics (I knew one). There are atheists that believe all sorts of weird things (railians, scientologists). There are even atheists that reject evolution. Atheists are individuals and individuals vary widely in their beliefs and opinions. The only thing all atheists have in common is the disbelief in a god.
Some are atheist for bad reasons (emotional reaction to bad religious experience), some for passive or neutral reasons, and some for good reasons (such as caring about the truth and knowing how to properly evaluate claims and evidence).
Being an atheist doesn't mean you make a positive claim that there are no gods. Reasonable atheists acknowledge that they cannot know for certain one way or the other. They simply haven't been convinced by any god claims. Being an atheist doesn't mean you're a hard nosed skeptic. It doesn't mean you're arrogant. It doesn't mean you're close-minded. You can find atheists with the above traits, but all atheists don't have them, just like all believers don't share the same traits.
Atheism is a rational position and perfectly compatible with humility and open mindedness. It's reasonable to not accept claims which have not met their burden of proof. Using evidence and reason is the best pathway to truth, not blindly accepting claims or making assumptions that fill some kind of void.
It's really popular to knock atheists and jump on the bandwagon by saying they're unreasonable arrogant snobs. This is part of the problem with the out of control discrimination against atheists in America. There is this stigma attached to the word "atheist" portraying them in a way that is unagreeable to everyone, and this needs to change.