"Mies was wonderful when he was asked how he went about designing the Seagram Building [1957-1958]. He said he read the New York City Building Code. I think that's an absolutely accurate and marvelous answer. It's what all of us do. You have to know what's possible. Architecture is not a question of the purely theoretical if you're interested in building buildings. It's the art of what is possible."
Rudolph, Paul Marvin, 1918-1997. "Interview with Paul Rudolph.". Ed. Robert Bruegmann. Chicago: Department of Architecture, Art Institute of Chicago, February 28, 1986.

http://www.artic.edu/aic/libraries/caohp/rudolph.pdf