I usually say that Atheism is not a belief system. That is, there is no positive claim within atheism which could lend to any particular system of belief. However, atheists need to be careful, especially those who say atheism is not a *belief (singular). In the past I too made the mistake of claiming atheism is not a “belief” in an of itself, but I have come to see that this reasoning is wrong. Atheism is, in fact, the belief that there are no gods.
Before you jump down my throat and try to explain Strong (Positive) atheism and Weak (Negative) atheism to me, let me inform you that I am not arguing about the definition of atheism, but rather, testing whether or not it fits the definition of what a Formal belief is.
If we find that atheism does fit the definition of a Formal belief, then we must be willing to admit that it has the properties of a belief. As such, it is important to make the distinction based on what analytic philosophers have defined as a Formal belief.
From the Stanford Encyclopedia of Philosophy:
Most contemporary philosophers characterize belief as a “propositional attitude”. Propositions are generally taken to be whatever it is that sentences express (see the entry on propositions). For example, if two sentences mean the same thing (e.g., “snow is white” in English, “Schneeist weiss” in German), they express the same proposition, and if two sentences differ in meaning, they express different propositions. (Here we are setting aside some complications about that might arise in connection with indexicals; see the entry on indexicals.)
A propositional attitude, then, is the mental state of having some attitude, stance, take, or opinion about a proposition or about the potential state of affairs in which that proposition is true—a mental state of the sort canonically expressible in the form “S A that P”, where S picks out the individual possessing the mental state, A picks out the attitude, and P is a sentence expressing a proposition.
As such, Atheism appears to be a belief in the non-existence of God, the rejection of theism, and the proposition that God does not exist.
This complicates matters when trying to define what atheism is, because having concluded that it is, in point of fact, a Formal belief, we can’t claim atheism isn’t a belief. In actuality, it is.
As such, if I were to ask you whether or not you believed in the Flying Spaghetti Monster, you would probably respond, “No.”
“Because there is no evidence for it.”
“Well,” I’d say, “That doesn’t prove the FSM doesn’t exist!”
“No, it doesn’t. But zero knowledge amounts to zero belief–I can’t honestly believe in something I know absolutely nothing about. Even if it did exist, my belief in it would be unfounded.”
“So you admit the FSM could exist!”
“It’s a possibility, but in order for me to believe in the reality that it exists, I would need to examine and test real evidence first. Something to prove the referent is real and not just imagined. Until then, the odds are equal to none that it’s imaginary.”
“You’re wrong! You just have to have faith!”
“I thought we were talking about facts. After all, you can’t believe in something that is imaginary, other than to believe it’s not real. In which case, you’d be an atheist just like me.”
This brings us back to Formal Beliefs. Proper beliefs usually depend on something being true, or having true properties, in order to be believed as true. For example, we cannot say we believe in delicious Smapples, because, to our knowledge, there is no such thing as a Smapple, hence no referent. Therefore we have no way to detect the truth properties of Smapples, delicious or not. The burden of proof would be on the person who thinks a Smapple is a real thing. They would need to produce one, so that their truth claim about the delectable quality of Smapples could be validated, or else, disproved.
Without providing a Smapple, however, we are only left with–well–nothing. No belief in the flavor of Smapples can be made based on nothing, and unable to imagine what a Smapple ought to taste like, it is impossible to claim we believe them, let alone believe them to be delicious.
Same goes for God. Atheism is simply the rational response to not being able to find any referent in reality which would qualify as God, and consequently formulating the belief that God does not exist.