His argument rests on the concept of the Rational Man, who must act consistently with his beliefs. But the history of Wall Street suggests that such consistency may be unwise. ... His ideal is a Rational Man equipped with a Perfect Computing Machine.... Of course, he admits that the Rational Man does not exist at all and that the Perfect Computing Machine will not exist in the foreseeable future, but the image of these nonentities seems to have colored his whole work and given it an air of fantasy 19 It was not even clear that what Markowitz had done counted as economics.

Donald MacKenzie, An Engine, Not a Camera, loc. 220