La plus belle théorie financière ne peut donner que ce qu'elle a

With the non-ending financial crisis, it is very easy to accuse research and financial theories for being responsible. For some people, these bad theories are destroying good management practices. The aim of this article is to say that the most beautiful theory can give only what she has and that the observed misgovernment of the financial system is not the sole responsibility of the lessons drawn from the financial theories. In a first part we start with a review of bad practices observed in finance (markets and corporate). Then, we analyse the impact of the theory on the bad practices. In a second part we show the limits of the financial theory and the need for a renewal taking in account the actual behaviour of people acting in finance. We also defend the idea that bad practices are encouraged with the growing complexity of the financial world.