The idea that the movements in the prices of financial securities are in some sense random and therefore that the mathematical theory of probability can be applied to them received its decisive development in the 1950s and the 1960s, but did not originate then. As financial markets blossomed in the nineteenth century, a popular "science of investing" developed and was incorporated into manuals of investment aimed at a readership of middle-class men with worries that investing in securities was gambling (Preda 2001 a, 2004a). In 1863, the French broker Jules Regnault published one such text. (See Jovanovic 2000; Jovanovic and le Gall 2001.) Regnault sought to demonstrate to his readers the distinction between gambling on securities and legitimate, patient longer-term investment. He applied a simple probabilistic model to show that those who made frequent bets on short-term movements in prices faced eventual inevitable ruin.

Donald MacKenzie, An Engine, Not a Camera, loc. 257