The museum has not been redefined so much as it has been disassembled, its coherence shattered as curators, administrators, and trustees grapple with the insoluble problem of operating in that nowhereland between art and life. Everything becomes the justification for everything else. The presence in the museum of Koons and Murakami is justified by relating their work to a taste for popular culture that goes back to such rock solid modern classics as Manet and Picasso. But Koons and Murakami—to the extent that they’ve learned most of what they know from Kmart and comic books—are also used to ratify Manet and Picasso, to give works that some believe are in danger of appearing superannuated a little street cred. And once you’ve embraced Kmart and comic books, why not Deitch’s shows dedicated to skateboards and graffiti? Of course I’m simplifying here. But there comes a time when we need to cut through the high falutin’ intellectual mind games that were featured in “High and Low: Modern Art and Popular Culture,” the landmark 1990 show at the Museum of Modern Art. Sometimes life is life and art is art. Why must everything always be mixed up? Why must it always be high and low?