Why atheism and not agnosticism? Such a question can provoke heated discussion among the non-believers. It seems that believers too try to weigh into the argument, selling atheism as unsound where agnosticism is the more prudent position. "The Great Agnostic" Robert G. Ingersoll would claim that atheism and agnosticism are one and the same, Bertrand Russell would distinguish between the terms depending upon his audience, and even Dawkins describes himself as an agnostic in the same way he's agnostic about fairies at the bottom of the garden.
The point being that whether atheism or agnosticism applies, the argument is drawn over whether one should ever use the word atheist. Now I'm perfectly happy to use the word even if I find it lacking. It's useful enough to get my point across and it is the closest word that sums up my position regarding the supernatural which would be understood by as many as possible.
But to use the word is to invoke claims of unreason; that it goes too far, that one is close minded, that one hasn't considered the possibilities, etc. Whether it is just or unjust criticism, it seems that for many there is an importance in refraining from declaring atheism and being part of the lesser agnosticism (depending on your definition of agnosticism). The two main challenges I see I present below.
The nebulous god
The first challenger is the liberal theist. Well I say liberal when I really mean the argument for God comes in an incredibly liberal form. It's correlated with the Abrahamic deity by name alone, but its form is so nebulous one wonders whether it could be called god at all.
Yet this is the god put forth and challenged, how could anyone deny such an entity? Well we can't, bring the term to such an abstract and it becomes meaningless. Such an entity is insoluble, an abstract that is beyond all knowledge and indeed possible knowledge. I can understand why Shermer uses agnostic in the Huxleyian sense, it's impossible to speak in anything but strong agnosticism when comprehension is beyond human understanding by very definition!
Of course in that sense agnosticism is preferable. But this is not the deity being questioned. In our society, it's the Judeo-Christian construct of God, and it has definite attributes. The nebulous deity has taken form and its that form on which we're asked to commit ourselves to. Of course it doesn't have to be the Judeo-Christian deity, any gods in any culture have the same property of defining the insoluble.
And what reason is there for this? Are we actually observing such a force in nature and measuring its properties? No, such claims are reverential in nature, or philosophically-reasoned inferences. In short, it's completely indistinguishable from the imagined. The gambit of any theist is that while all other gods in all other cultures are products of deluded minds, their god truly revealed itself to its followers.
These revealed gods ultimately rest on an act of faith, and it's an act of faith that flies in the face of human psychology and sociology. How can it be that we are not projecting our agency detection software onto the universe? How can it be that one culture is right while all others are deluded when all are using the same brain? I see no reason to be agnostic towards any of these cultural gods because they all try to claim knowledge that is unobtainable. The nebulous god? Yes. Zeus? No.
The other challenger is the agnostic atheist. And most of them are weak atheists, it's not that they are doubting theists. But for some the argument is that strict agnosticism in the non-Huxleyian sense should be maintained because we can't disprove that God exists. It seems that atheists could argue among themselves for hours over which word to use without getting anywhere, yet still have almost equal philosophical positions.
This is my defence of the use of the word atheist.
It seems there are many reasons to avoid the term itself; that in some places it is equivalent to baby rapist, that it is taken as an a priori dismissal of the possibility of gods, that it's constructed to be a world-view, that it takes an untenable position on the unknowable.
As linked above, I draw a parallel to what it means to be a non-astrologer. If someone asks me if I believe in astrology, i say no. I don't fall into a quasi-rant where I explain that while I can't disprove astrology I see no reason to believe that there's any correlation between the movement of the planets and stars to events of individuals and societies on this planet, let alone causation. I just say no, I don't believe in astrology. I have no reason to and the only reason I'm asked whether I do is because a portion of the population does.
So why can't it be the same when involving gods? Perhaps it's the supernatural component. So while astrology may be paranormal, the criticism of astrology can be done involving this reality. Thus I'm building up one huge straw man and making a categorical error. This falls back on the insolubility problem outlined above.
Even to take the most extreme definition of atheism: a denial of God, it doesn't mean that it falls into an a priori dismissal. It also doesn't mean that one isn't open to the possibility of there being god(s) as real entities. To use an example, take ghosts.
At one time I believed in ghosts, I thought they were real, that humans would linger on after death and be able to "haunt" people. And over time I ended up losing that belief, now I'm pretty sure that ghosts don't exist. Does this mean that I dismiss ghosts out of an a priori? No. Does it mean that I'm now fixed forever with a denial of something I can't disprove? Again, no. Show me strong evidence that ghosts do indeed exist and I'll change my mind.
Perhaps it would be best to be teapot agnostics, that is agnostic in only the sense that one can't disprove gods in the same sense that one can't disprove there's a teapot orbiting between Earth and Mars. This distinguishes it from the standard use of agnosticism which really boils down to doubtful theism, qualifying the use of the word in denial but of the greatest standard of disproof.
Atheism, I feel, has come to entail that very position. I'd say the bulk of atheists I've met would be teapot agnostics, not claiming to have disproved god but have no reason to believe in god beyond the futility of not being able to disprove the concept. They think the idea of gods silly, myth born out of human culture and thought processes, yet would not claim to know gods don't exist. This is the new atheism.