Towards Design Theory and expandable rationality : The unfinished program

It is said that Herbert Simon would have described himself as follows : «I am a monomaniac. What I am a monomaniac about is decision making ». In spite of its shares of legend and humour, this self-portrait deeply reflects the main logic of Herbert Simon’s works. From his early papers on administrative behaviour to his last investigations on thought and learning, Simon kept a same goal : to explain complex and mysterious human behaviour by simple and constrained, yet informed, decision rules. « Bounded rationality » was the name he gave to a research orientation wich rejected the maximizing behaviour assumed by classic economics. But beyond this critical aim, Simon attempted to build an empirically grounded theory of human problem solving. A theory that was intended to settle the foundation stone of « behavioural economics ».