where do ideas come from?

From an interview with Italian architect Renzo Piano (of Paris' Centre Georges Pompidou fame, which he designed with Richard Rogers), in Metropolis magazine:

When you visit buildings by other architects, what do you look for?
Haha! First, I enjoy them very much. Second, I steal everything. Stealing is maybe too hard a word. There’s an Italian word, you say “rubarro,” which means a nice robber, without a mask.

What did T.S. Elliot say, “Good poets borrow, great poets steal”?
It’s really about that. But art is about that. Music is about taking and giving back. In a way I spend my entire life stealing from everything—from the past, from cities I love, from where I grew up—grabbing things, taking not only from architecture but from Italy, art, writing, poetry, music. And you know what, I put all my robberies in a little piece of paper that I have with me and fill almost a whole sketch pad. Even when I don’t like a building, I still find something to take. This is probably because I was never a good school boy, so I grew up with the idea that I was not the first in class and I was a problem all the time. When you grow up with that idea, you spend your life taking from others.