 It may be objected that the use of the parameter \(c\) is not really needed in the definition of the Peirce-function. Clearly, it has no role to play neither in (a)–(e) nor in (g). The parameter is in fact used in (f), but this may be said to be rather unimportant, since as indicated above necessity is in fact incorporated in the Peircean notion of future. Based on such considerations Prior (1967, p. 132 ff.) showed that the Peircean models may in fact be defined in terms of a simpler Peirce-function without any reference to the parameter \(c\) (i.e. the chronicles), if it is assumed that (f) can be left out of the Peircean system in question. The main advantage of keeping the extended formalism, is that it facilitates its comparison with the system to be presented in section 5.1.