I'll tackle the first two questions... Warhol's message with his seriographies like the Campbell's soup cans piece was that anything, however banal, could be elevated to icon/high art status if it was properly labeled as "art". I wish I could say that this issue is entirely debatable, but it isn't... Warhol's seriographies as worth a fortune, and for good or ill (I leave it up to you to weigh in on this for yourself), Warhol has earned his place in the long history of art...
What was Warhol saying about American society? That it was like a naive child that liked bright shiny trinkets and could be conned into buying into the idea that while a can of soup was not art, a straigh foward illustration of one was, if all parties could agree that this was so. Incidently. The actual idea for the painting was not his own.
This is what Warhol had to say about Coca Cola after painting a bottle of coke as a subject:
"What's great about this country is that America started the tradition where the richest consumers buy essentially the same things as the poorest. You can be watching TV and see Coca-Cola, and you know that the President drinks Coca-Cola, Liz Taylor drinks Coca-Cola, and just think, you can drink Coca-Cola, too. A Coke is a Coke and no amount of money can get you a better coke than the one the bum on the corner is drinking. All the cokes are the same and all the cokes are good. Liz Taylor knows it, the President knows it, the bum knows it, and you know it."
Re. Duchamp's influence: Well... Duchamp was the first artist to exploit the notion of the found object elevated to art by exhibiting a urinal in a gallery and declaring it a work of art. Duchamp, like Warhol, liked to play with the notion of APPEARENCES and DOUBLE ENTENTE... note Duchamps drawing of a pipe with the caption: "Ceci n'est pas une pipe"... which begs the question what is "une pipe"? If you understand French, then you will know that idiomatically, "une pipe" can signify something other than a smoking pipe. Kids read these posts, so I won't elaborate further.
Differences... Andy Warhol was perhaps more reliant on other people for actual inspiration, but he was by far a better business man. Warhol's true genius, in my view, lies not in his skill as an artist (which was really not that great, but this is a matter of opinion, and probably has more to do with my general dislike of his work than his actual skill) but rather in his knack for recognizing and exploiting trends that define the ZEITGEIST... the spirit of the times, and then capitalizing on the trend better than anyone else. No artist understood the power of branding better than Warhol.
J.E. Raddatz // www.jeraddatz.com