One of the more common criticisms I've heard directed at atheists is that in order to be an atheist, one must claim to know everything that exists in the universe and beyond. That is, in order to claim that no gods exist, one must possess all knowledge about everything that could possibly exist. Since obviously no human could possibly know everything that exists, it is argued that atheists are simply dishonest and arrogant.
While there may be atheists who make such claims, the vast majority do not. This is actually a misunderstanding of atheism on the part of believers who offer this criticism. The majority of atheists do not in fact assert that no gods exist. Most are actually agnostic, and simply remain unconvinced that any particular god exists.
However, in this article I want to go a bit further and put forward some arguments for why it may well be more rational to believe that no gods exist, at least for all practical purposes.