Is atheism a belief?

[Belacqua]

Atheism is not a belief, positive or negative. Just like someone who knows that the earth is round does not merely believe that the earth is round.

Well, the shape of the earth is pretty hard for reasonable people to deny. (Though I know that there are currently unreasonable people who do so.) 

As so often in discussions like these, we end up getting fuzzy about what "belief" and "knowledge" mean. 

So for example, a Christian can say he knows that there is a God, because as far as he's concerned there is indisputable evidence. (revelation, authority, tradition, logical arguments in natural theology and metaphysics) 

You and I would say he merely believes there is a God, because we think his evidence is bad. 

But you see the problem here: the words end up being defined by what we think constitutes good evidence. 

That's why in philosophy the standard definition of knowledge is as a subset of belief. A belief is anything we hold to be true, and knowledge is stuff we hold to be true that are also justified and (really are) true. 

It may well be that things we are well justified in believing turn out in the long run not to be true. For example, for a long time doctors had good reason to say that stomach ulcers are caused by stress. Then somebody discovered h. pylori, or whatever that bug is called, and it turned out that what they thought was knowledge was actually belief. They believed it entirely in good faith, but oops, they had to change their minds. 

Naturally, we are very very well justified in believing certain things (e.g the shape of the earth, evolution) and I have no hesitation in calling them knowledge. But they are still that subset of things I believe which are also (I'm quite sure) true. 

I might take a look at some claim made by theologians, such as the idea that the Christian God is much like the Platonic Form of the Good. After some thought, I might conclude that this claim is silly. I would then believe that it's not a persuasive claim, and may be dismissed--to me, I think I know that. A better philosopher than I, however (not difficult to find one) might follow the argument better, and conclude that my reasoning is wrong and what I hold to be knowledge is really belief. And then we would have to fight it out. 

So I guess I'm just not comfortable making this clear distinction between belief and knowledge as if they were wholly different. 

(And for all the picky people out there, I know there are also Gettier cases.)