 Given that “[t]he concept of successive applications of an operation is equivalent to the concept ‘and so on’” (5.2523), one can see how the natural numbers can be generated by repeated iterations of the general form of a natural number, namely ‘[\(0, \xi , \xi +1\)]’. Similarly, truth-functional propositions can be generated, as Russell says in the Introduction to the Tractatus (p. xv), from the general form of a proposition ‘[\(\overline{p}\), \(\overline{\xi}\), \(N(\overline{\xi})\)]’ by 