Since Paul Samuelson died recently there has been much talk about how he shaped modern economics and, his influence on most of the branches. As far as I have been able to read, the emphasis is usually put on mathematics and how he helped to make economics looking more like other hard sciences with its complex formal apparatus. My opinion is a bit different; I think Samuelson’s main contribution was to create a method of which mathematics was just one component and, maybe more importantly, he solved one of the most important methodological problems of our beloved dismal science: he created the theory of revealed preference. In this article I will try to sketch in a nontechnical way why it is so important and what are its consequences.

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