Having shown the irrelevance of capital structure and of dividend policy in their simple assumed world, Modigliani and Miller then investigated the consequences of allowing some more realism (especially in regard to taxes) back in. Just how far to go in adjusting their model to "reality" and the exact consequences of doing so became matters of dispute between Modigliani and Miller. Attuned, as Keynes had been, to the imperfections of markets, Modigliani was the more cautious. Indeed, when first describing the irrelevance of capital structure to a class at Carnegie Tech, he distanced himself: "I announced the theorem and said `I don't believe it."' (Modigliani interview) Miller, in contrast, was prepared more radically to set aside the question of the validity of assumptions, in the manner advocated by Friedman (Miller interview).

Donald MacKenzie, An Engine, Not a Camera, loc. 187