What It Means to Say I'm an Atheist

I haven't really stated it unequivocally before, partly because I wasn't sure of myself and partly because I just didn't want to admit it. But I've done some thinking, and I think I should lay it out clearly rather than beating around the bush:

I'm an atheist.

There. Now that I've said it, I'm going to unpack that statement by explaining what it does and does not mean.

It Does Mean...

Well, in itself, it means very little: simply that I don't believe in God. Or to put it more carefully, I lack belief in any deity. That's all there is to it. In practice, however there are several related principles that atheists often (but not always) hold. For example:

I value reason as the best tool we have for evaluating the world around us.
I see science as a highly effective application of our reasoning ability.
I am skeptical of extraordinary claims, religious or otherwise.
I try to reject dogmatic and irrational thinking in all its forms.
I am also agnostic, meaning I think the existence of God can't be conclusively proven or disproven.

It Doesn't Mean...

This list is much longer, mainly because there are so many faulty assumptions about atheism. For example, the fact that I'm an atheist does not mean that:

I'm absolutely certain I'm right: Certainty is no more a requirement for atheists than it is for theists. I think there's a small chance that a god of some sort exists, but that doesn't mean I'm not an atheist.
I need to prove God doesn't exist: It is theists, who make the positive claim that "God exists," who have the burden of proof. Most atheists simply see insufficient evidence for the theist claim.
I have "faith" in my position: Curiously, theists see the atheist's alleged faith as a bad thing—whatever happened to faith being a virtue? Anyway, faith is belief apart from evidence—some theists may agree and some may protest, but this is inevitably what it amounts to in practice. My position is based on an examination of the evidence, so I don't have "faith" in the religious sense.
I claim to have all the answers: I don't. Neither theists nor atheists know the answers to every important question we face. The difference is that theists often claim to, while atheists admit that they don't know and keep searching.
I'm rebelling against God out of hatred or selfishness: This is just silly. I spent more time agonizing over this process than anything else I've ever done. I've had to give up my hope of heaven, and I constantly worry about how my friends and family will react. Besides, I don't even believe in God. To say I'm rebelling against him makes no more sense than to say that Christians are rebelling against Ganesha.
I never truly believed in Christianity in the first place: Interestingly, this is almost the opposite of the last misconception. The fact is that I fully believed by any reasonable definition of the term "belief." If we apply this question to other religions (e.g. Were Muslims who deconvert never really Muslims at all?), its absurdity should hopefully become evident even to Christians.
I have no reason to be moral: First of all, religious motivations to be good—the threat of hell, the promise of heaven and divine command theory—are terrible to start with. Second, humans have an innate sense of empathy. That doesn't magically disappear when you become an atheist. Third, secular ethical systems do exist, and from what I've seen, some provide a much better basis for morality than religions do.
My life is no longer worth living: I'll be the judge of that, thanks. Theists often denigrate earthly happiness as fleeting and therefore empty, but if anything the opposite is true. If my time is limited, I should enjoy it all the more while it lasts, whether it be by spending time with loved ones, savoring a great meal, or staring up at the stars in awe, pondering life's great mysteries.
I can't be convinced that I'm wrong: I'm certainly open to changing my mind, but to provide good arguments for theism isn't enough: they must also outweigh the good arguments against it. And to claim the existence of a being with God's extraordinary traits requires equally extraordinary evidence.

So that's what it means (and doesn't mean) to say that I'm an atheist. I didn't suddenly change into some cold, uncaring monster once I stopped believing in God. All I did was apply my reasoning abilities to an area of my life where I had previously suspended them. I still love my family, and I still enjoy the same things I used to—it's just that now I appreciate it all a little bit more.