 Temporal logic was introduced by Arthur Prior (see for instance Prior 1967). Here we will sketch only propositional temporal logic (for a more thorough introduction the reader is advised to consult Gamut 1991: chapters 2 and 3) and the entry on  temporal logic.    Temporal logic introduces operators \(\bG\), \(\bH\), \(\bF\) and \(\bP\), which are similar to the modal operators \(\Box\) and \(\Diamond\). We summarize the intuitive meaning of these operators in Table 1. 