 If \(a\) and \(b\) are two problems, then \(a \wedge b\) designates the problem “to solve both problems \(a\) and \(b\)”, while \(a \vee b\) designates the problem “to solve at least one of the problems \(a\) and \(b\)”. Furthermore, \(a \supset b\) is the problem “to solve \(b\) provided that the solution for \(a\) is given” or, equivalently, “to reduce the solution of \(b\) to the solution of \(a\)” \(\ldots \neg a\) designates the problem “to obtain a contradiction provided that the solution of \(a\) is given” \(\ldots(x)a(x)\) stands in general for the problem “to give a general method for the solution of \(a(x)\) for every single value of \(x\)”. (Kolmogorov 1932: 59 [Mancosu 1998: 329])