Efficient-market theorists agreed with fundamentals analysts that securities had an intrinsic value that was rooted in the reality of the economic situations of the corporations that issued them. However, efficient-market theory posited that market prices were the best available estimators of that intrinsic value: that was part of the meaning of the statement that "prices always `fully reflect' available information" (Fama 1970, p. 383). Corporate fundamentals mattered, but, precisely because there were many skilled and intelligent analysts scrutinizing their implications for stock prices, such implications would already have been incorporated into prices. In consequence, if markets were efficient, fundamentals analysts were wasting their time looking for cases in which intrinsic value differed knowably from market price.

Donald MacKenzie, An Engine, Not a Camera, loc. 342