David Durand rejected capital-structure irrelevance before Modigliani and Miller published it

Evidence

Despite these incipient disagreements, Modigliani and Miller found themselves on the same side with respect to traditional finance scholarship, just as they had with respect to Herbert Simon’s critique of orthodox economic reasoning. Their sharpest dispute was with David Durand, a prominent finance scholar of a more traditional, institutional bent who held a professorship of industrial management at MIT. Durand had himself examined what was in effect Modigliani and Miller’s proposition about the irrelevance of capital structure, and had at least hinted that arbitrage might in principle enforce it. Ultimately, however, he had rejected the proposition. — Donald MacKenzie, An Engine, Not a Camera, 189

Categorization

• XREF: Durand’s institutionalist rejection — but with a hint that arbitrage could enforce irrelevance — prefigures the performativity question: whether arbitrage needs to be actually practiced or merely modeled for the theorem to work.