In March 2008 Kees Kaan, of Claus and Kaan Architects, gave his inaugural lecture as Practice Professor of Architectural Design at Delft Technical University – the school from which he graduated in 1987. He explained to his audience that after his student years spent designing imaginary projects he most wanted to design in order to build, to make ‘designs that were thicker than paper’. This was accomplished in 1987–97 in intensive daily co-operation with Felix Claus and then developed over the last decade in their offices in Amsterdam and Rotterdam with new partners. The following is an edited extract from his lecture where, after discussing practice, education, societal interest and the changed architectural market of the Netherlands, he turned to architectural vision, understanding and responsibility.