Does God Practice a Random Walk? The ‘Financial Physics’ of a Nineteenth-Century Forerunner, Jules Regnault

We analyse the work of a neglected French economist, Jules Regnault, whose Calcul des Chances et Philosophie de la Bourse (1863) laid the basis of modern stochastic models of price behaviour and contains an anticipation of econometrics. At a time when short-term speculation was denounced as immoral, he approached this question ‘scientifically' and constructed two models. The first one was relative to short-term speculation and took the shape of a random walk – a model used by Bachelier (1900). The second one deals with long-term speculation and aims at evaluating the mean value of the French 3 per cent bond