A. N. Prior. Tense-logic and the continuity of time. English, with Polish and Russian summaries. Studia logica, vol. 13 (1962), pp. 133–151. - R. A. Bull. An algebraic study of Diodorean modal systems. The journal of symbolic logic, vol. 30 (1965), pp. 58–64. - A. N. Prior. Postulates for tense-logic. American philosophical quarterly, vol. 3 (1966), pp. 153–161.

1967 ◽  
Vol 32 (2) ◽  
pp. 245-246
Author(s):  
Alan Ross Anderson
Keyword(s):  
Tense Logic ◽  
Symbolic Logic ◽  
Modal Systems

On finite and infinite modal systems

1938 ◽  
Vol 3 (2) ◽  
pp. 77-82 ◽  
Author(s):  
C. West Churchman
Keyword(s):  
Modal Logic ◽  
Symbolic Logic ◽  
Modal Operator ◽  
Image Position ◽  
Modal Systems ◽  
Complex Modal

In Oskar Becker's Zur Logik der Modalitäten four systems of modal logic are considered. Two of these are mentioned in Appendix II of Lewis and Langford's Symbolic logic. The first system is based on A1–8 plus the postulate,From A7: ∼◊p⊰∼p we can prove the converse of C11 by writing ∼◊p for p, and hence deriveThe addition of this postulate to A1–8, as Becker points out, allows us to “reduce” all complex modal functions to six, and these six are precisely those which Lewis mentions in his postulates and theorems: p, ∼p, ◊p, ∼◊p, ∼◊∼p, and ◊∼p This reduction is accomplished by showingwhere ◊n means that the modal operator ◊ is repeated n times; e.g., ◊3p = ◊◊◊p. Then it is shown thatBy means of (1), (2), and (3) any complex modal function whatsoever may be reduced to one of the six “simple” modals mentioned above.It might be asked whether this reduction could be carried out still further, i.e., whether two of the six “irreducible” modals could not be equated. But such a reduction would have to be based on the fact that ◊p = p which is inconsistent with the set B1–9 of Lewis and Langford's Symbolic logic and independent of the set A1–8. Hence for neither set would such a reduction be possible.

Prior’s Turn to Medieval Logic

KronoScope ◽  
2022 ◽  
Vol 21 (2) ◽  
pp. 157-171
Author(s):  
David Jakobsen
Keyword(s):  
Tense Logic ◽  
Symbolic Logic ◽  
Important Lesson ◽  
Modern Logic ◽  
Medieval Logic ◽  
Truth Value ◽  
Present Tense

Abstract The peculiar aspect of medieval logic, that the truth-value of propositions changes with time, gradually disappeared as Europe exited the Renaissance. In modern logic, it was assumed by W.V.O. Quine that one cannot appreciate modern symbolic logic if one does not take it to be tenseless. A.N. Prior’s invention of tense-logic challenged Quine’s view and can be seen as a turn to medieval logic. However, Prior’s discussion of the philosophical problems related to quantified tense-logic led him to reject essential aspects of medieval logic. This invites an evaluation of Prior’s formalisation of tense-logic as, in part, an argument in favour of the medieval view of propositions. This article argues that Prior’s turn to medieval logic is hampered by his unwillingness to accept essential medieval assumptions regarding facts about objects that do not exist. Furthermore, it is argued that presentists should learn an important lesson from Prior’s struggle with accepting the implications of quantified tense-logic and reject theories that purport to be presentism as unorthodox if they also affirm Quine’s view on ontic commitment. In the widest sense: philosophers who, like Prior, turn to the medieval view of propositions must accept a worldview with facts about individuals that, in principle, do not supervene (present tense) on being, for they do not yet exist.

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