The show's most notable absence may be Marcel Duchamp. The arbitrariness of Duchamp couldn't have happened without the dose of willfulness to be found in any Cézanne...To his many enemies, Cézanne seemed to put the whole world--not to mention the entire history of art--through a blender. Duchamp merely turned one toilet upside down.
I don't think Blake means to say what it sounds like he's saying here. Actually...Blake, what are you saying here? That Duchamp's entire oeuvre boils down to one readymade? Remember The Large Glass? Nude Descending a Staircase? The demented Origin of the World-inspired lifesize diorama that is L'Etant Donnés? Love him, hate him, or profess indifference, you at least have to admit that he tried on a lot of hats--and did a bit more over the course of his career than upend a urinal.
Enough has already been said about Blake and one-liners that just don't work. I think Regina got it right when she explained why he's so poorly served by Twitter, for example, and I should probably leave it at that.
But c'mon. You were at the Philadelphia Museum. I haven't been there in awhile, but unless the Duchamp Gallery was closed, it seems to me there should have been more than enough of the man's work on view--like, say, the entire Arensberg collection--to facilitate considering him more carefully.