Carroll Quigley was a legendary teacher at the Georgetown School of Foreign Service. His course on the history of civilization was extraordinary in its scope and in its impact on his students. Like the course, The Evolution of Civilizations is a comprehensive and perceptive look at the factors behind the rise and fall of civilizations. Quigley defines a civilization as "a producing society with an instrument of expansion." A civilization's decline is not inevitable but occurs when its instrument of expansion is transformed into an institution—that is, when social arrangements that meet real social needs are transformed into social institutions serving their own purposes regardless of real social needs.