An Observation Concerning Porte’s Rule in Modal Logic

It is well known that no consistent normal modal logic contains (as theorems) both ◊A and ◊¬A (for any formula A). Here we observe that this claim can be strengthened to the following: for any formula A, either no consistent normal modal logic contains ◊A, or else no consistent normal modal logic contains ◊¬A

Two Temporal Logics of Contingency

This work concerns the use of operators for past and future con-tingency in Priorean temporal logic. We will develop a system namedCt, whose language includes a propositional constant and prove that(i) Ct is complete with respect to a certain class of general frames and(ii) the usual operators for past and future necessity are denable insuch system. Furthermore, we will introduce the extension Ctlin thatcan be interpreted on linear and transitive general frames. The theo-retical result of the current work is that contingency can be treatedas a primitive notion in reasoning about temporal modalities

Two Temporal Logics of Contingency

This work concerns the use of operators for past and future con-tingency in Priorean temporal logic. We will develop a system namedCt, whose language includes a propositional constant and prove that(i) Ct is complete with respect to a certain class of general frames and(ii) the usual operators for past and future necessity are denable insuch system. Furthermore, we will introduce the extension Ctlin thatcan be interpreted on linear and transitive general frames. The theo-retical result of the current work is that contingency can be treatedas a primitive notion in reasoning about temporal modalities

Freedom and causality in contemporary Islamic & Western philosophy

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