David Jakobsen

'Wolterstorff (2009) provides an important explanation to the question: What caused the surprising resurgence in philosophical theology that has occurred over the last 50 years—a resurgence that rivals its zenith in the Middle Ages? This article supplements that with a more fine-grained answer to the question. Recent discoveries in Arthur Norman Prior’s correspondence with J.J.C Smart and Mary Prior, between November 1953 and August 1954 on the possibility of necessary existence, demonstrates the importance of Prior’s discussion of the Barcan formulae in Time and Modality (1957) for the resurgence of analytic theology. The correspondence establishes that Prior’s discovery of tense-logic, and his discussion of quantified tense-logic constituted the perfect opportunity for him to challenge key anti-metaphysical assumptions in analytic philosophy, from which four important consequences can be drawn for the resurgence of philosophical theology. First, Prior’s discussion of time and existence challenged the idea of Russell (1945) and Findlay (1948) on the logical status of a necessary existing being. Second, the discussion challenged the Analytic school’s view of analysis and gave Prior the opportunity to introduce a different perspective on the relationship between logic and metaphysics. Third, it gave Prior a good opportunity to demonstrate that the then-prevailing attitude towards medieval logic was wrong. Fourth, it made it possible for Prior to demonstrate that the highly surprising metaphysical conclusions of quantified tense-logic brings modern logicians into a discussion with the theologically minded medieval logicians.

Arthur Norman Prior (1914 – 1969) and Georg Henrik von Wright (1916 – 2003) both attended a conference in England sometime in the spring of 1956, after which they corresponded on Anselm’s ontological argument. Prior had at the conference presented a formal treatment of the ontological argument. Based upon notes from the Prior archive at the Bodleian Library, and correspondence with von Wright, we here presents Prior’s and von Wrights’ discussion of Anselm’s argument in light of Prior’s published, as well as unpublished writings on the ontological argument. Three versions of the ontological argument from Prior’s unpublished as well as published papers is presented: a non-modal, an argument from possible existence and finally a modal version. While Prior dismissed the first on the basis of a meta-theorem for proof in argumentation, the second on the basis of a fallacious commutation of operators, he argued that a valid version of the ontological argument can be proven from the distinctive S5 thesis of Lewis modal logic. While Prior gave reasons for a rejection of those distinct S5 thesis, in favour of Lewis S4 system, he also provided a novel argument in favour of accepting the S5 thesis for necessity and possibility. Finally we relate Prior’s work to Plantinga (1974) and consider objections raised by Oppy (2012) and Gale (2007) toward the modal versions of the ontological argument.

In his philosophy, William of Ockham (1285-1347) offered an important and detailed response to the classical argument from the truth of a statement regarding the future to the necessity (unpreventability) of the statement. In this paper, Ockham’s solution and the possible formalisation of it are discussed in terms of modern tense and modal logic. In particular, the famous branching time formalisation suggested by A.N. Prior (1914-19) is discussed. Weaknesses and problems with this suggestion are pointed out, and an alternative formalisation of Ockham’s solution without the use of branching time is presented.

Arthur Norman Prior (1914-69) was a logician and philosopher from New Zealand who contributed crucially to the development of ‘non-standard’ logics, especially of the modal variety. His greatest achievement was the invention of modern temporal logic, worked out in close connection with modal logic. However, his work in logic had a much broader scope. He was also the founder of hybrid logic, and he made important contributions to deontic logic, modal logic, the theory of quantification, the nature of propositions and the history of logic. In addition, he discussed questions of ethics, free will, and general theology. Prior’s philosophical works comprise about 200 titles. His earliest articles center on philosophical theology and historical studies of Scottish Reformed Theology. This led on to the publication of his first influential work on ethics: Logic and The Basis of Ethics (1949). With the invention of tense-logic in the early 1950s, his focus shifted to investigations into the syntax of tempo-modal logic leading to his seminal Time and Modality (1957), a volume derived from his John Locke Lectures in Oxford in 1956. Furthermore Prior, together with the Irish mathematician and logician C.A. Meredith (1904-76), made important early contributions to the semantics of possible worlds. Prior’s tense-logic provided a strong conceptual framework for problems pertaining to the philosophy of time. In Time and Modality, Prior discussed the philosophical implications of Ruth Barcan’s famous formulae for tense-logic, and in the 1960s he worked on the notion of the present. The most persistent problem running through Prior’s work is his study of the questions surrounding human freedom and divine foreknowledge, and more general philosophical problems emerging from this classical theological question. His thorough analysis of this problem, with the conceptual tools of tense-logic, received a crucial impetus from his correspondence with the young Saul Kripke, when the latter suggested the semantic tool of branching time to Prior. Prior’s development of two solutions based on branching time for the problem of future contingency, the Peircean and the Ockham solution, was most thoroughly developed in Past, Present and Future (1967), the most important work published by Prior. Characteristically for Prior’s methodological approach, the development of these two solutions were at the same time a development of two new systems of tense logic, and vice versa. One of Prior’s significant contributions to logic was his work on world propositions and instant propositions. In the course of developing these notions he also made one of the earliest formulations of hybrid logic. In Papers on Time and Tense (1968), he presented this idea in a more detailed manner in the context of his four grades of tense-logical involvement.

On the historic Cross, it is God Himself Who has actually met the last dark limits of our life, and has brought Himself face to face with that inescapable something (or Someone) which seems to keep us forever strangers (physically, morally, logically and in every other way) to the Absolute and Eternal. And because it is God Himself Who has thus in life and in death personally encountered sin, death, time and corruption, He has overthrown them and raised and transformed the existence that is subject to them, our existence, into the glorious Being of His Everlasting Godhead. He has robbed death of its sting and the grave of its victory, and delivered us from Satan's ancient power. A.N. Prior: Athanasius Contra Mundum. Prior (1934)

Logic has sometimes been seen as an alternative to metaphysics and to speculation. In this paper it is argued that a different story should be told when it comes to temporal logic and tense-logic in particular. A. N. Prior’s first formulation of tense logic was mainly established in order to qualify the discussion of certain metaphysical and conceptual problems. Although temporal logic has now been developed in various abstract and rather technical ways, it may still serve as a great help for anyone who wants to clarify the discussion of important existential questions like the nature of time, determinism, future contingency or freedom of choice.

Logic has sometimes been seen as an alternative to metaphysics and to speculation. In this paper it is argued that a different story should be told when it comes to temporal logic and tense-logic in particular. A.N. Prior’s first formulation of tense logic was mainly established in order to qualify the discussion of certain metaphysical and conceptual problems. Although temporal logic has now been developed in various abstract and rather technical ways, it may still serve as a great help for anyone who wants to clarify the discussion of important existential questions like the nature of time, determinism, future contingency or freedom of choice.