 In his dissertation of 1907, Brouwer still accepted PEM as a tautology, (mis)understanding \(A \vee \neg A\) as \(\neg A \rightarrow \neg A\) (Brouwer 1907: 131, 160 [1975: 75,  88]).[7]  Curiously, he did realize at the same time that there is no evidence for the principle that every mathematical proposition is either provable or refutable (Brouwer 1907: 142n.3 [1975: 101]); this principle is the constructively correct reading of PEM. In the paper from 1908, he corrected his earlier understanding of PEM: