The use of demonstrations provided scholars from diverse disciplines— notably philosophers and economists—an unusual opportunity to observe possible flaws in their own thinking. Having seen themselves fail, they became more likely to question the dogmatic assumption, prevalent at the time, that the human mind is rational and logical. The choice of method was crucial: if we had reported results of only conventional experiments, the article would have been less noteworthy and less memorable. Furthermore, skeptical readers would have distanced themselves from the results by attributing judgment errors to the familiar l the famifecklessness of undergraduates, the typical participants in psychological studies. Of course, we did not choose demonstrations over standard experiments because we wanted to influence philosophers and economists. We preferred demonstrations because they were more fun, and we were lucky in our choice of method as wel as in many other ways. A recurrent theme of this book is that luck plays a large role in every story of success; it is almost always easy to identify a smal change in the story that would have turned a remarkable achievement into a mediocre outcome. Our story was no exception.