The effects of the use of the Black-Scholes-Merton model in arbitrage thus seem to have formed a direct performative loop between "theory" and "reality." Markets were, however, also changing toward greater conformity to the model for reasons in which the model was not directly implicated. In 1973, Black, Scholes, and Merton's assumptions were wildly unrealistic. Stock, for example, could not be bought entirely on credit: it had been the constraint this placed on market makers' capacity to hedge using stock that Rissman had been trying to have removed during his unsuccessful visit to the Federal Reserve.

Donald MacKenzie, An Engine, Not a Camera, loc. 739