Semper Fiasco
Just for shits and giggles...
Theist: I believe that the universe was created by Oprah last week. Don't try and convince me otherwise; I have faith!
Atheist: I cannot believe that the universe was created by Oprah last week unless you can show me some sound evidence to back up your claims.
Agnostic: Well, there's really no way to be sure whether the universe was created by Oprah or not. We can't prove it was, and we can't prove it wasn't. It might have been... but I'm not sure.
I believe the form of Agnosticism Tarquin Aluclaire is talking about is the mentality that they have no reason to believe in a god, but if soild evidence were to be presented, the would believe.
Now, I know that sounds an awful like like the definition of Atheism you provided. But I have
personally found that the definitions between the two are often blurred. I have told many people what I believe to be true and people come to different conclusions as to what I am. My views are that if testable evidence of god were to be shown, I would believe it. And while I consider myself an Atheist, seeing how no testable proof of god has ever been shown, I have been told that my views are actually defined under Agnosticism. It's odd and somewhat aggravating that it's still a blurred line even after a definition has been assigned, but it happens quite often.