Eugene Volokh asks why people care so much about swearing, and gets at more-or-less the right answer. (Once upon a time obscenity and profanity were bound up in all the typical anxieties about sex, religion, and fecal matter, for all your typical social and psychoanalytic reasons. Plus, swearing signals anger and rage, which is scary.)

Whatever, though. What I want to know is why people care so much whether thieves steal "priceless" works of art. Okay, no, that's obvious. The real question, I guess, is why people care so much about the original version of a work of art. From the standpoint of a casual museum-goer—from the standpoint of anyone aside from carbon-daters and hardcore historians—it's pretty irrational to care whether I'm seeing the original, authentic version of Edvard Munch's The Scream or a perfect-yet-bogus replica. The clever forgeries usually match up with the original as far as brush-stroke and color goes, so even aspiring young artists who want to "learn" from examining a masterpiece can get all they want out of looking at a high-quality copy. Nevertheless, I care. But I shouldn't.

Obviously some people have a very high stake in making sure that people do care. Museums, for instance, need to offer some sort of value to justify their high ticket prices, and that value is their unique ability to say "here be originals!" They could lie, of course, but it's not likely that the secret could be kept for very long. Art dealers, meanwhile, want people to value originals so that they can restrict the supply of their goods and earn more on their sales; otherwise they may as well just be selling trinkets on the sidewalk. And the artists themselves probably need people to care about authenticity, since it provides a sort of copyright protection on their work, which can finance or provide an incentive for innovation. (Although it's odd that we value an original work of visual art so highly, but will happily listen to cheap knock-offs of musical recordings, for instance. Why are the two industries set up so differently in that regard?)

Anyway, that still begs the question: why should anyone care whether a piece of art is "authentic" or just a perfect-yet-bogus replica? Eh, that's probably a question for psychoanalysis: fear of the double and all that. Or maybe as with profanity, concern about authenticity in art has to do with class and status—technically, I could flaunt the fact that I've seen the original "Mona Lisa," and all you rabble who haven't made it out to Paris have not. Nowadays, I would sound like a real chump if I said that, but at one point it might have been worth doing. And of course, people don't always care about the originals—too much. Fake art circulates through art auctions all the time, and dealers aren't thrilled with the fact, no, but they'll still places their bids, and won't take every precaution in the world to make sure a $15,000 Monet was, in fact, painted by Monet. Very odd.