 Intuitionistically, to say that a proposition \(A\) is true is primarily to say that we have effected a construction that is correctly described by \(A\); the proposition \(A\) is made true by the construction. Idealizing to a certain extent, we say that \(A\) is true if we possess a construction method that, when effected, will yield a construction that is correctly described by \(A\). According to Brouwer, to say that a proposition \(A\) is false then must mean that it is impossible to effect an appropriate construction; notation \(\neg A\). Such an impossibility is recognized either immediately (e.g., the impossibility to identify 1 unit and 2 units) or mediately. In the former case, one observes directly that an intended construction is blocked; it “does not go through” (Brouwer 1907: 127 [1975: 73]). In the latter case, one shows that a proposition \(A\) is contradictory by reducing \(A\) to a known falsehood, e.g., one shows that \(A \rightarrow 1=2\) (Brouwer 1954A: 3). In practice, one defines \(\neg A := A \rightarrow 1=2\) (and hence \(\neg 1=2\) is seen as a particular case of \(A \rightarrow A)\).