Commenter extraordinaire Ben Bateman deconstructs relativism in the comment thread of my earlier post about evil.
Mark: You seem to be using a weird liberal rhetorical device. Driving home, sometimes all I can get on the radio is Alan Colmes, and he does this all the time:
"You say X. But other people say Y. So how can we know?"
The implication is that we can't really know anything until everyone with expertise on the subject holds to a single view. This is impossible, of course, for anything but the most basic of logical truths, so it amounts to the claim that we can never really know anything. It thus amounts to a species of relativism.
As with all types of relativism, this argument is a weapon rather than a belief. For example, I have never heard a liberal say: "Sure, I think that taxes should be higher. But some conservatives disagree. So who really knows?" No, it is always the conservative belief that must dissolve into relativistic mud at the mere hint of a contrary liberal belief.
Mark puts up a good fight and the comments are better than my post, so go read them.