 Then it follows that \(n\not\in X\) if and only if \(f(m,n)=1\) for some natural number \(m\), which implies that \(f\) cannot be computable. For if so, the complement of \(X\) would be computably enumerable, implying the computability of \(X\). Since \(f\) is a function from the intuitionistic point of view, this establishes that in Intuitionism not all functions are computable. 