Where have all the atheists gone?
Gone are the days of Friedrick Nietzche, Jean-Paul Sartre, and Bertrand Russel. These were the atheists that were bold enough to make the claim that "God does not exist". Today, atheists wouldn't dare utter that phrase (with rare exception and failing miserably: see here, 1:19:00 - 1:25:00). Today, atheism is regarded as merely a "lack of belief" in God, something I've heard repeated ad nauseam. Dan Barker, president of the Freedom from Religion Foundation, commented that "basic atheism is not a belief. It is the lack of belief. There is a difference between believing there is no god and not believing there is a god—both are atheistic, though popular usage has ignored the latter."
As a former agnostic, it should be noted that a "lack of belief" is more consistent with agnosticism as agnostics have no firm commitment to either statement that God does or does not exist. In fact, it's become popular to redefine traditional atheism into two categories: "weak" and "strong" atheism. "Weak" atheism, referred to as agnostic atheism, does not believe in God, but also does not claim to know this is true. Whereas, "strong" atheism, or gnostic atheism, believes God does not exist and claims to know this is true. A "lack of belief", ironically, falls into the category of "weak" atheism.
I think redefining atheism in this way is in error, but we'll leave that aside for the moment.
Why is this important?
Why is it important to understand what is meant by "lack of belief"? For the fact that this form of atheism makes no claim about the reality of God's existence or non-existence, only that the individual holds no belief in God. It is argued that atheism (as defined as a "lack of belief") is the default position. So, if an argument for God fails or is unconvincing, the individual is said to be justified in resorting back to the default position: a "lack of belief".
You might be asking yourself, "How can anyone be a default atheist if there is no positive evidence that atheism itself is true?" Ah, this is where things get clever. You see, amongst those who have debated God's existence (or any topic for that matter) it's understood that the onus is on the individual making a positive claim. That means, for anyone who claims X does or X does not exist, they must substantiate their claim. Since a "lack of belief" makes no claim about the existence or non-existence of God but simply their personal psychological condition, there is no onus on the atheist to substantiate their "lack of belief".
Clever, right?
Clever, but...
Yes, clever. But, also telling.
It's clever because it's a semantic move that removes the requirement to substantiate their position. After all, they're merely stating their personal psychological condition (e.g. I'm not persuaded by your argument), but they're not making a claim about whether God actually exists or not. The onus, then, is solely on the theist making the positive claim that God does exist.
It's telling because it's a tacit admission that the claim "God does not exist" cannot be substantiated (or, at least, the "weak" atheist will not put forth any effort in doing so).
Some atheists might claim, "Well, you can't prove the non-existence of something" as justification for their "lack of belief" position, but this is also incorrect. You can show the non-existence of something by showing that the concept of that thing is logically contradictory. For instance: I can prove that there are no married bachelors. I can prove that there are no one-ended sticks. I can prove that there are no square circles. These things are logically contradictory, so, a priori proof that they do not exist.
Historically, atheists attempted to do the same thing with the concept of God (e.g. the Omnipotence Paradox, the Problem of Evil, Justice vs Mercy paradox, etc.). Of course, as each of those objections were addressed, the atheist, much to their chagrin, has been backed into a cognitive padded room. Thus, all we are left with are atheists that "lack belief". It's an intellectual copout and a psychological safe space.
An Intellectual Copout
Just as there are "weak" atheists who do not claim to know if God exists or not, so are there "weak" theists who do not claim to know if God exists or not. So, to use Dan Barker's definition, then, those theists would "lack belief that there is no God" (forgive the double-negative, but you get the point). Using that definition, there is no longer an onus on the theist either! Whether you are an agnostic atheist or an agnostic theist, it seems strange to hold a position of which you have no positive reasons to believe is true. It's as if we've created a category in which people have been given permission to stop thinking.
Epistemic vs Ontological
Here is where these "lack of belief" atheists makes their biggest error. They confuse the epistemic question of God's existence with the ontological question. A "lack of belief" is an epistemic position (i.e. one's subjective psychological condition). The ontological question (i.e. an objective claim about things existing in reality) still remains; does God exist? It is probably the most fundamental question anyone can ask and attempt to answer. The answer does not have to conclude with 100% certainty, but simply plausibility. Is it more plausible that God exists or does not exist? Now, why is that? Answering those questions moves you beyond mere "lack of belief" and into the forbidden zone: intellectually engaged.
So, How Should Atheism Be Defined?
In the Stanford Encyclopedia of Philosophy, philosopher Paul Draper examines several definitions of atheism across the philosophical spectrum and this is what he concludes:
J. L. Schellenberg says that “in philosophy, the atheist is not just someone who doesn’t accept theism, but more strongly someone who opposes it.” In other words, it is “the denial of theism, the claim that there is no God” (2019: 5).
Robin Le Poidevin writes, “An atheist is one who denies the existence of a personal, transcendent creator of the universe, rather than one who simply lives his life without reference to such a being” (1996: xvii).
In the Concise Routledge Encyclopedia of Philosophy, William L. Rowe (also an atheist) writes, “Atheism is the position that affirms the nonexistence of God. It proposes positive disbelief rather than mere suspension of belief” (2000: 62).
The Cambridge Dictionary of Philosophy recognizes multiple senses of the word “atheism”, but is clear about which is standard in philosophy:
[Atheism is] the view that there are no gods. A widely used sense denotes merely not believing in god and is consistent with agnosticism [in the psychological sense]. A stricter sense denotes a belief that there is no god; this use has become standard. (Pojman 2015, emphasis added)"
There has been significant effort in avoiding the standard definition of atheism (just read some of the atheists blogs that talk about a "lack of belief"). I get it, taking a philosophical position of which there is no positive evidence or arguments is difficult to sustain and defend. So, creating a category of atheism of which requires no justification is understandable. However, for those who appreciate the intellectual discussion, atheism is not the default position. Atheism makes a positive claim: the belief that there is no God or gods. As such, that claim requires justification and substantiation. Don't let them squirm out of their share of the burden of proof.