Bringing finance theory into confrontation with reality turned out to be a complex matter. The results of empirical testing were often equivocal, and argument broke out over whether the Capital Asset Pricing Model could be tested at all. The efficient-market hypothesis seemed empirically the sturdiest of finance theory's central propositions, but it too began to encounter anomalies. "Reality" was not a stable backdrop against which testing could take place: finance theory's effects on its object of study were growing.

Donald MacKenzie, An Engine, Not a Camera, loc. 388