For if the Zeitgeist was technology, then steel and glass structure was necessarily the appropriate form of modern building for the modern city, especially the modern American city. Since this conclusion was arrived at “rationally,” there was no room for caprice or for “self-expression” in the building art properly practiced.
“Architecture,” Mies would declare over and over in America, “is not a cocktail.”
And even if one sensed the arbitrariness of his way of defining rationality, it was difficult to argue the point in the sight of those walls at IIT, which looked so incontrovertible in their structural logic, largely because they were given form by so unimpeachable an artistic sensibility."
— Franz Schulze, Mies Van Der Rohe: A Critical Biography