Is atheism a belief?

[Belacqua]

How do you differentiate things you hold to be true which are beliefs from things you hold to be true which are rational conclusions?

Things which I rationally conclude are true are beliefs. Things which I rationally conclude are untrue are disbeliefs. A disbelief is not a belief. Absence of belief is not a belief.

https://www.define-atheism.com/

The question I'm working on here is: by what standards do you reach these beliefs? 

I hold that you have intellectual commitments according to which you make judgments. These are the tools or standards by which you accept or reject religious claims. Therefore, in your case, your atheism is a lack of belief (in God) which is determined by your belief in other things. 

I don't know exactly what these other things are, in your case. If I made a guess, I'd say it's something to do with the type of evidence which you believe is worthy of being believed. It's common, for example, to say that repeatable empirical evidence is more trustworthy, while revelation or scripture is less trustworthy.

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As me (Grandizer), I have very good reasons for consciously not accepting theism.

That's good. It's good to be aware of the standards and reasons by which we accept or reject things.

But that's not what makes me (or anyone) an atheist. What makes an atheist an atheist is their lack of belief in god, and that is it.

And I am only claiming that people who hear and reject religious claims tend to do so for reasons. The reasons they have may of course vary.

I can certainly concede that there are probably atheists who do not judge religious claims according to any standards. They just reject all such claims out of habit or bigotry. These people are prejudiced non-thinkers. I hope that no one like that is posting here.

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Just to be as clear as I can, let me give an additional example.

Let's imagine a certain atheist, whom I'll call Possible Atheist A. I'll try to make him a believable example.

PAA believes that the collected works of science give us the most reliable way of knowing about the world. Not perfect, perhaps abstractly phenomenal in some Kantian way, but the best knowledge that we have. He believes that since the Bible was written a long time ago when people were less knowledgable about scientific topics, the Bible is not a reliable source of information about the world. And since, as far as he knows, science gives no evidence at all for the existence of God, he sees no reason to believe in God. He lacks belief in God for these reasons.

So he is a textbook atheist: he lacks a belief in God. But how did he get to that position? His position is based on his belief that science is pretty reliable and the Bible isn't. If his beliefs were different, his conclusion might be different.

So he is an atheist whose lack of belief in God relies on, or derives from, logically prior beliefs about evidence and its relation to the world.

I feel that this is a standard example of how thinking people come to lack belief in God.