If you want to do economics well, you at least need to be a decent mathematician. When still at high school, I was warned by my teacher that most economics faculties had one requirement: an above average grade for mathematics. Fair enough, I thought, given the fact that economics is full of equations and statistics. The mathematical approach of economics, however, has not always been the only bar in town. How then, did economics become so obsessed with mathematics? And is this obsession still justified?