Myth:
The only rational position is that of the agnostic because there can be no rational proof of God's existence or nonexistence.
Response:
It's popular for self-proclaimed agnostics, and more than a few theists who aren't agnostics, to proclaim that agnosticism is more rational and reasonable than atheism. Sometimes agnostics may also include theism as being less rational, but typically atheism is the only target. This reveals the underlying problem: the goal is simply to attack atheism, not to make a case for agnosticism, so both atheism and agnosticism are misrepresented to make the latter look more sensible than the former.
Undogmatic Agnosticism?
One of the most significant aspects of agnosticism that draws people to it is the perception that it is relatively undogmatic and reasonable in comparison to other options. It does not claim to have certain knowledge about the nature of universe because it starts from the premise that we limited humans don't know a great deal and probably know far less than we realize. Such a starting point seems to many to be entirely fair and rational.
This perception, however, has led people to make unjustified assumptions about the nature of atheism and theism. Thinking that agnosticism is some sort of "middle ground" between the two, those drawn to agnosticism have made the leap to assuming that both atheism and theism are necessarily dogmatic, unyielding, and thus irrational. The problem is that people simply don't understand that agnosticism addresses a different question from the other two and, therefore, cannot qualify as a "middle ground" between them.
Reasonable Agnosticism?
Sometimes people claiming that only agnosticism is reasonable do so based on the idea that we can't "know" if God exists because we can't perform any experiments on it — but that too is a mistake. It's wrong to claim that something isn't "knowledge" unless you can run a repeatable experiment on it. That's a standard for scientific knowledge, not knowledge in the general sense. In general, something can qualify as "knowledge" when it's a "justified, true belief." Obviously a repeatable experiment is a great way to justify a belief, but it's not the only way. There are cases where we can't perform an experiment to test something, but you are still justified in believing it and it's still true. Therefore, it counts as knowledge.
The ability to test the claim "god exists" depends entirely upon how we define "god" — under some definitions an experiment may be possible; under others, it won't be. In the cases where no test is possible, it's unlikely that the claim being made is meaningful and, therefore, an agnostic position on such a god probably isn't justified. Why be "agnostic" about an alleged god that isn't described or defined very well or very coherently? We have to conclude, therefore, that however reasonable agnosticism might be generally, there are definitely situations where it isn't.
Agnosticism, Theism, and Atheism
Agnosticism is about knowledge — an agnostic takes the position that they don't know if any gods exist or not, perhaps that they cannot know if any gods exist or not, and in some cases that no human being can possibly know if any gods exist or not. Saying "I don't know" can indeed be a reasonable answer to the question of what one knows, but neither atheism nor theism address the question of what one knows — they address the question of what one believes.
Theists believe in the existence of at least one god of some sort and atheists don't. That's it — that's all there is to mere theism and mere atheism. Both atheists and theists may be dogmatic, unyielding, or irrational in what they believe or don't believe. Then again, they may not. There's nothing about either that demands it. Both atheists and theists may be agnostics as well — whether one believes or disbelieves, one may do so in the context of not claiming to know for sure one way or the other.
Theists Defending Agnosticism
The most curious source of this myth must be theists who aren't themselves agnostics. Somehow, some theists have gotten it into their heads that it makes sense to argue that agnosticism is more reasonable than atheism even though the implication of this argument is that they, as theists, are in the same boat as atheists. On one level it might be said that pointing this out is just a tu quoque fallacy — even if the theist is guilty of the same problem, this doesn't excuse atheists and doesn't constitute a rebuttal.
Given the rebuttals above, though, it does become legitimate to wonder why theists would try to make an argument that would, if valid, paint them as being just as unreasonable as the atheists they are trying to critique. Do they really think that they are unreasonable and should become agnostic theists? I doubt it. I don't think that they actually believe their own argument that agnosticism is truly more reasonable than atheism.
Instead, I think they hope that if they can convince atheists to become agnostics (under their false definitions of atheism and agnosticism), then they will be one step closer to being converted to some conservative, evangelical brand of Christianity. What this means then is that such theists are employing an argument not because they think it's valid, but rather because they think it will serve their ideological agenda. They don't care about truth, facts, or logic; instead, all they care about is getting more people to agree with their religion.
