 Note that in the Peircean temporal logic, the formula \(\varphi \rightarrow HF\varphi\) is no longer valid, which blocks the Master Argument of Diodorus Chronus: what is the case now need not have been necessary in the past. Moreover, while Peirceanism preserves bivalence and the principle of excluded middle \(\varphi \vee \neg\varphi\), it renders all formulae expressing future contingents false and hence invalidates the principle of future excluded middle \(F\varphi \vee F\neg\varphi\). This principle states that eventually either \(\varphi\) or \(\neg\varphi\) will be the case and is usually judged intuitively valid (see e.g. Thomason 1970).