Published in 1965, Boyd’s The Puzzle of Architecture surveys post-war international architecture and the tension between main-line functionalism and more expressive, sculptural design. Boyd takes Eero Saarinen as a key example, describing the Miesian functionalism of GM Technical Centre and reflecting on Saarinen’s move towards a more sculptural approach in the Kresge Auditorium and Yale Hockey Rink. Boyd highlights the TWA Terminal, completed in 1962, as emblematic of this tension, questioning the authenticity, reasonableness and architectural success of this highly sculptural and expressive building. Boyd also reflects on changes in building technology, particularly the possibilities and limitations of thin-shell concrete, as highlighted by the changing structural design of Jørn Utzon’s Sydney Opera House.