Thanks for your detailed response Tommy. I think we can agree on the definitions of religion that you brought up, and I understand your position that Christianity encompasses those and adds the extra element of the personal relationship. I think I first saw that concept expressed as such in the book Fast Facts on False Teachings by Ron Carlson.
However I would like to respond to your assertion that atheism can be considered a religion as well by points 3 and 4. I think you are completely wrong on that and would like to take a moment to comment. This is something I see fairly often, it's called an equivocation fallacy, and is a big misunderstanding of atheism. It's like when I hear people that are not religious or Christian but also don't identify as atheist accuse atheists of being just as dogmatic as fundamentalist Christians.
Atheism is most definitely NOT a set of beliefs, has nothing to do with values, and is not a worldview of any kind. It is merely the lack of belief in a god or gods. In the same way that you (I assume) do not believe that unicorns exist, that does not encompass an entire worldview and set of values for you. Now granted, atheism may play a part, along with many other aspects, of a particular worldview but in and of itself atheism is not a religion or set of guidelines. You can take five atheists and easily discover they have widely varying beliefs and values. This point is a real biggie, so I wanted to make [sure] I spent enough time to make it clear. If you get this point you'll be much more effective in speaking knowledgeably about the topic to both fellow Christians and non-believers.
Definition #4 has even less application to atheism. Although some atheists, like me, take an active interest in dialoguing about atheism and theism, it's by no means a principle we are devoted to or obsessed with. Many atheists, including myself, are open to the possibility of God existing and would change their minds *given sufficient evidence* (and for various reasons creation, or the universe itself, is not proof, but that's another discussion). That is the key detail as we are not credulous and cannot take certain details "on faith." If their is something we (and even then I can't speak for all atheists - many believe all kinds of nonsense but just don't happen to believe in God) are devoted to it is skeptical inquiry and critical thinking. And if skeptical inquiry and critical thinking leads to God, so be it, but so far for the majority who have applied it rigorously it doesn't.
I hope that is helpful to you.
You said, "Atheism is most definitely NOT a set of beliefs." I have to, once again, disagree with that. I think it is. Please allow me to explain my position.
You see, do you or do you not believe that God does not exist? If you say you believe He doesn't exist, you have just admitted to me that you actually do have a belief. Also, you have to believe that this world got here somehow. Whether you believe that it was always in existence or came from sludge, you do believe something about the world's existence.
Next point. You said, "Although some atheists, like me, take an active interest in dialoguing about atheism and theism, it's by no means a principle we are devoted to or obsessed with." I don't know you personally, therefore, I have to believe that you are not obsessed with defending atheism. However, I know someone who is (well, I actually just know of him). His name is Richard Dawkins.
Richard Dawkins travels all around the world talking about Darwinian evolution. I assume you are familiar with Ray Comfort (I believe most atheists probably are). If not, you can learn more about him by accessing one of his sites, LivingWaters.com, through my blog (just click the link on my sidebar). Anyhow, Ray Comfort recently (about seven months ago) published a version of The Origin of Species, revealing the flaws of evolution, and handed them out free of charge at many of America's top universities. When Richard Dawkins became aware of that, he instructed students to accept the books, but to rip out the extra fifty pages that Ray Comfort had written. If Dawkins is not devoted to evolution, then why was he so concerned about the books?
Lastly, you said, "Many atheists, including myself, are open to the possibility of God existing and would change their minds *given sufficient evidence* (and for various reasons creation, or the universe itself, is not proof, but that's another discussion)." Are you really open to the possibility of God's existence, or are you just saying that because you are convinced that He doesn't exist and you'll never have to actually change your mind? If you are, let me ask you this: if you found out that God really does exist, would you be willing to change your lifestyle to suit His standards? If so, I know how you can get the evidence that you need. Just comment on this post, letting me know that you are willing, and I will let know how you know how you can find the infallible proof that you need.
You seem to be an intelligent guy. I pray that what you said is true, and that you are open to God's existence. If so, that is the first step to the hope of Heaven. Thank you so much for your comment!
Hope you have a great weekend!