  In “The Unreliability of the Logical Principles” of 1908, Brouwer formulates, in general terms, his criticism of PEM: although in the simple form of \(p \vee \neg p\), the principle will never lead to a contradiction, there are instances of it for which one has, constructively speaking, no positive grounds. Brouwer names some. Because they do not in the strict sense refute PEM, they are known as “weak counterexamples”. See the supplement on Weak Counterexamples.