Just asking, part 2.

I wrote about atheists last week, but didn't realize that the billboard I saw was for an actual meeting here in Des Moines for a bunch of atheists. I read an article in the paper as to why they were meeting, which if you remember, puzzled me. As it turns out, according to this article, they want to organize so they can influence legislation that supports their beliefs. I guess I understand that, but here is a question that came up. On WHAT, do you base those beliefs on? Most documents that were written to found this country, are based on Biblical principles. Like it or not, God is mentioned in most. So my question is, do the atheists have something to base their beliefs on? Scientologists have the writings of L. Ron Hubbard. The Mormons have the Book of Mormon. Is there a book of atheism? Perhaps there is an "atheism for Dummies" I could take a look at. I'm not interested in converting, just interested on what makes you an atheist. Is it just a non-belief in God? No idea. There was another group that was included on the billboard, unless the name was just another name for atheists, and it was freethinkers. I'm not sure what that is, but it sounds good. Can you be a freethinker AND part of a group? If you are thinking free, I guess that doesn't mean you are alone, it's a hard title to decipher. I wonder if they have a book?