What's the idea behind the Mona Lisa?
Of course, there's that whole sticky wicket of Platonic forms , in which the object (the execution of the idea) is just a flawed imitation of the true idea.
(But I hate to sidetrack the thread into a debate over materialism -- although I think the mathematics point was spot on...)
Of course, in reality, Scott was probably a little frustrated that some fans were shooting down a movie before they had ANY IDEA whatsoever about it -- and here the rest of us spend our time debating his idea about their lack of an idea. If ideas are worthless, what are ideas about ideas?