What is Art? Pt 1

The precursor to what is Theatre, I think it's time I try and define Art. What is it? Where are the boundaries between Art and, well, not-art? Things that masquerade as art, say, crass commercial movies or theatre?

But then what about Pop Art? Found Art? Can I hang Duchamp out to dry?

I'm at the Metropolitan Museum of Art to come up with an answer. More on this as events warrant.
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