my coffee cup spoke to me

On the side of my Starbucks coffee cup (apparently they're not all hippies after all):

Everywhere, unthinking mobs of "independent thinkers" wield tired cliches like cudgels, pummeling those who dare question "enlightened" dogma. If "violence never solved anything," cops wouldn't have guns and slaves may never have been freed. If it's better that 10 guilty men go free to spare one innocent, why not free 100 or 1,000,000? Cliches begin arguments, they don't settle them.
-Jonah Goldberg
Editor-at-large of National Review Online

I think about this theme all the time. Political cartoons, quotes, and any sort of piece of art is the same thing. You can't use these things as evidence. Those things present ideas, they don't really add weight to an argument. I mean sometimes they can, because you're borrowing credibility from a great mind or an expert, but in most cases, citing a quote from some book isn't a valid piece of evidence in an argument. Art and cliches are meant to inspire, not to answer.