Atheism is not a "belief system"[/B]
Atheism
noun
1. the doctrine or belief that there is no God.
2. disbelief in the existence of a Supreme being or beings.
Atheism | Define Atheism at Dictionary.com
Atheism is by defintion a belief. It certainly isn't based on any form of logic.
How is it logical to believe there is no God? The only possible way to know there isn't a God is if you were everywhere at the same time and at all times. In otherwords, in order to prove there is no God you would have to be a god.
What is reasonable then? I only see two options.
1) You don't know if there is a God or not. You freely admit you don't know there is a God, but recognize that since you can't possibly prove that there isn't one, you leave open the possibility that there is one. We can call this a reasonable agnostic. We can just call it neutral. Doesn't really matter. The danger with this option is that many who adopt agnosticism also adopt the pressumption that because you don't know, no one knows and no one can ever know. That is where agnosticism becomes unreasonable.
2) You know there is a God because of personal exeriences and through eye witness encounters with Diety. At which point it becomes completely unreasonable to ever think there is no God.
So summary, the only reasonable positions about the existence of God is 1) Don't know but possible. or 2) Do know through personal experience.
Anything else is just a belief that may or may not be correct. Which is the problem with atheists and atheism. They think they are reasonable when by every definition of the word, their assumptions are only beliefs and can only ever be beliefs.
The problem with using reason as a basis for belief is that most people have no clue what reason actually is. And there is absolutely nothing wrong with belief at times.