Y a-t-il une théorie des marchés financiers ?.

Ever since the Creation of the stock exchange, scientists have tried to endow them with a theoretical representation. Mathematicians endeavoured to demonstrate that the Gaussian character of financial markets should by necessity neutralise any speculative temptation. Astrophysicists went further by referring to the brownian mouvement. However, economists observe that these markets go alternatively through phases of euphoria and depression. Thus, the question to be asked is to know «how to beat the market». Some, taking recourse to covariance analysis, recommend portfolio diversification ; others prefer a reflex interaction between players and the market ; others again establish their theories upon their own experience by being particularly attentive to the intrinsic value of the enterprise, thus drawing a strong dividing line between the investor and the speculator. Gradually, the range of theoretical constructions widens as far as to include chaos on one side and gregarian behaviour on the other. Will the recent introduction of ethical indexes be able to eliminate the doubts concerning the possibility of truly theorizing financial markets ?.