 In order to define the Peircean models according to Prior’s first attempt, it is assumed that there is a valuation function, TRUE, which gives a truth-value (0 or 1) for any propositional constant at any moment in TIME. On this basis, the valuation function of a Peircean model, \(\Peirce(t,c,p)\) can be defined recursively for any wff \(p\), any moment of time \(t\) and any chronicle \(c\) with \(t \in c\):