Lately I have become convinced that twentieth-century architecture was first and foremost an architecture of in situ concrete. People are likely to claim that skyscrapers of steel-frame construction were the representative buildings of the twentieth century, but I do not believe that was the case. Buildings constructed of in situ concrete are the form of architecture that is most free and universal, and that form was most in keeping with a century whose primary objectives were freedom and universality. Steel-frame construction may have been more delicate and transparent than concrete construction but was a distant second to concrete as far as freedom and universality were concerned.