Arthur Norman Prior (4 December 1914 – 6 October 1969), usually cited as A. N. Prior, was a New Zealand–born logician and philosopher. Prior (1957) founded tense logic, now also known as temporal logic, and made important contributions to intensional logic, particularly in Prior (1971).
Arthur Norman Prior  

Born  Masterton, New Zealand  4 December 1914
Died  6 October 1969 Trondheim, Norway  (aged 54)
Education  University of Otago (B.A., 1935; M.A., 1937)^{[1]} 
Spouse(s) 

Relatives  Ian Prior (halfbrother) 
School  Analytic philosophy 
Institutions  Canterbury University College 
Academic advisors  J. N. Findlay^{[1]} 
Doctoral students  Max Cresswell Kit Fine 
Other notable students  Genevieve Lloyd^{[6]} Jonathan Bennett^{[6]} Richard Routley 
Main interests  
Notable ideas 

Influenced

Prior was born in Masterton, New Zealand, on 4 December 1914, the only child of Australianborn parents: Norman Henry Prior (1882–1967) and his wife born Elizabeth Munton Rothesay Teague (1889–1914). His mother died less than three weeks after his birth and he was cared for by his father's sister. His father, a medical practitioner in general practice, after war service at Gallipoli and in France—where he was awarded the Military Cross—remarried in 1920. There were three more children, the first: epidemiologist, Ian Prior. Arthur Prior grew up in a prominent Methodist household. His two Wesleyan grandfathers, the Reverends Samuel Fowler Prior and Hugh Henwood Teague, were sent from England to South Australia as missionaries in 1875.^{[7]} The Prior family first moved to New Zealand in 1893.
While studying for his B.A. degree at the University of Otago, Prior attended the seminary at Dunedin's Knox Theological Hall but decided against entering the Presbyterian ministry and began to focus on logic. He married Clare Hunter, a freelance journalist, in 1936, and they spent several years in Europe, during which they tried to earn a living as writers. Daunted by the prospect of an invasion of Britain, he and Clare returned to New Zealand in 1940.^{[1]} At this point in his life he was a devout Presbyterian, though he became an atheist later in life.^{[8]}^{[9]}
After divorce from his first wife, he remarried in 1943 to Mary Wilkinson, with whom he would have two children. He served in the Royal New Zealand Air Force from 1943 to 1945 before embarking on an academic career at Canterbury University College in February 1946. His first position was a lectureship which had become available when Karl Popper left the university.^{[10]}
After returning to New Zealand following a year at Oxford as a visiting lecturer he took up a professorship in 1959 at Manchester University where he remained until he was elected a Fellow of Balliol College, Oxford in 1966 and appointed a Reader. He continued his Manchester practice of accepting visiting professorships.^{[10]}
Arthur Prior went to give lectures at Norwegian universities in September 1969 and on 6 October 1969, the night before he was to deliver a lecture there, he died from a heart attack at Trondheim, Norway.^{[10]}
Prior was educated entirely in New Zealand, where he was fortunate to have come under the influence of J. N. Findlay, ^{[1]} under whom he wrote his M.A. thesis on 'The Nature of Logic'.^{[11]} While Prior was very fond of the theology of Karl Barth, his early criticism of Barth's adherence to Philosophical Idealism, is a mark of Findlay's influence on Prior.^{[12]}
He began teaching philosophy and logic at Canterbury University College in February 1946, filling the vacancy created by Karl Popper's resignation. In 1951 Prior met J. J. C. Smart, also known as "Jack" Smart, at a philosophical conference in Australia and the two developed a lifelong friendship. Their correspondence was influential on Prior's development of tense logic. Smart adhered to the tenseless theory of time and was never persuaded by Prior's arguments, though Prior was influential in making Smart skeptical about Wittgenstein's view on pseudorelations.^{[13]} He became Professor in 1953. Thanks to the good offices of Gilbert Ryle, who had met Prior in New Zealand in 1954, Prior spent the year 1956 on leave at the University of Oxford, where he gave the John Locke lectures in philosophy. These were subsequently published as Time and Modality (1957). This is a seminal contribution to the study of tense logic and the metaphysics of time, in which Prior championed the Atheorist view that the temporal modalities of past, present and future are basic ontological categories of fundamental importance for our understanding of time and the world. Prior was several times warned by J. J. C. Smart against making tenselogic the topic of his John Locke lectures. Smart feared that tenselogic would get Prior "involved in side issues, even straight philosophy, and not in the stuff that will do Oxford most good."^{[14]} Prior was however convinced that tenselogic had the potential to benefit logic, as well as philosophy, and thus he considered his lectures an "expression of a conviction that formal logic and general philosophy have more to bring to one another than is sometimes supposed".^{[15]}
During his time at Oxford, Prior met Peter Geach and William Kneale, influenced John Lemmon, and corresponded with the adolescent Saul Kripke. Logic in the United Kingdom was then in a rather low state, being "deeply out of fashion and its practitioners were isolated and somewhat demoralized."^{[16]} Prior arranged Logical a Colloquium which brought together such Logicians as John Lemmon, Peter Geach, Czesław Lejewski and more.^{[17]} The colloquiums were a great success and, together with Prior's John Locke lecture and his visits around the country, he helped revitalize British logic. ^{[18]} From 1959 to 1966, he was Professor of Philosophy at the University of Manchester, having taught Osmund Lewry. From 1966 until his death he was Fellow and Tutor in philosophy at Balliol College, Oxford. His students include Max Cresswell, Kit Fine, and Robert Bull.
Almost entirely selftaught in modern formal logic, Prior published four major papers on logic in 1952,^{[19]} when he was 38 years of age, shortly after discovering the work of Józef Maria Bocheński and Jan Łukasiewicz,^{[20]} despite very little of Łukasiewicz's work being translated into English.^{[21]}^{[22]} He went so far as to read untranslated Polish texts without being able to speak Polish claiming "the symbols are so illuminating that the fact that the text is incomprehensible doesn’t much matter".^{[23]} He went on to employ Polish notation throughout his career.^{[24]} Prior (1955) distills much of his early teaching of logic in New Zealand. Prior's work on tense logic provides a systematic and extended defense of a tensed conception of reality in which propositional statements can change truth value over time. ^{[25]}
Prior stood out by virtue of his strong interest in the history of logic. He was one of the first Englishspeaking logicians to appreciate the nature and scope of the logical work of Charles Sanders Peirce, and the distinction between de dicto and de re in modal logic. Prior taught and researched modal logic before Kripke proposed his possible worlds semantics for it, at a time when modality and intentionality commanded little interest in the English speaking world, and had even come under sharp attack by Willard Van Orman Quine.
He is now said to be the precursor of hybrid logic.^{[26]} Undertaking (in one section of his book Past, Present, and Future (1967)) the attempt to combine binary (e.g., "until") and unary (e.g., "will always be") temporal operators to one system of temporal logic, Prior—as an incidental result—builds a base for later hybrid languages.
His work Time and Modality explored the use of a manyvalued logic to explain the problem of nonreferring names.
Prior's work was both philosophical and formal and provides a productive synergy between formal innovation and linguistic analysis.^{[citation needed]} Natural language, he remarked, can embody folly and confusion as well as the wisdom of our ancestors. He was scrupulous in setting out the views of his adversaries, and provided many constructive suggestions about the formal development of alternative views.
The following books were either written by Prior, or are posthumous collections of journal articles and unpublished papers that he wrote:
He was, at this stage of his life, obsessed with religion. He believed in the virgin birth and the voice of the devil, and was a devout Presbyterian (Prior 1940)...In later life, however, he described himself as having ‘no religious beliefs’ (Prior c.1967). In 1961, when Max Cresswell—then a logic student aged 21—met him for the first time, in Manchester, Prior announced: ‘Mr Cresswell, isn’t it a pity that God does not exist’.
He was influenced for several years by the theologian Arthur Miller, who combined a strict adherence to Presbyterian doctrine with an equally strong support for socialism and opposition to nationalism. But Prior's pacifism weakened, and he served from 1942 to 1945 in the New Zealand air force. And the central focus of his interests gradually shifted  helped by an occasional bout of atheism  from theology to ethics and logic.
Of the four technical papers that marked the explosive beginning of Prior’s career as a formal logician in 1952 (1952ad), two concerned modal logic...His one recourse in the face of isolation was to read, and read he did. In logic he began by returning to W.E. Johnson. Next came J.N. Keynes’s Studies and Exercises in Formal Logic and then (in his own phrase) he got stuck into Principia Mathematica. He learned a lot about the history of the subject from Peirce, whom he found ‘unexpectedly magnificent’. An important discovery, in 1950, was Bochenski’s Précis de Logique Mathematique (Bochenski 1949). Prior was fascinated by the ‘very neat symbolic notation’ due to Łukasiewicz, and before long he turned his back completely on the more usual PeanoRussell notation
This paper was the curtain raiser to Prior’s extensive study of Łukasiewicz’s work on modality, and thereafter he read Łukasiewicz widely...To judge by his references in The Craft, his first encounters with modern symbolic modal logic must have been the pioneering explorations by Lewis in his and Langford’s Symbolic Logic, Bochenski’s chapter ‘La Logique de la Modalité’ in his La Logique de Théophraste, and Feys’ article ‘Les Systèmes Formalisés des Modalités Aristotéliciennes’...An important discovery, in 1950, was Bochenski’s Précis de Logique Mathematique (Bochenski 1949). Prior was fascinated by the ‘very neat symbolic notation’ due to Łukasiewicz, and before long he turned his back completely on the more usual PeanoRussell notation.
This paper was the curtain raiser to Prior’s extensive study of Łukasiewicz’s work on modality, and thereafter he read Łukasiewicz widely—even material in Polish, saying ‘the symbols are so illuminating that the fact that the text is incomprehensible doesn’t much matter’.
...It must have stood high in the author's own estimation, for in 1995 he began translating it into English.
This paper was the curtain raiser to Prior’s extensive study of Łukasiewicz’s work on modality, and thereafter he read Łukasiewicz widely—even material in Polish, saying ‘the symbols are so illuminating that the fact that the text is incomprehensible doesn’t much matter’.
Prior was fascinated by the ‘very neat symbolic notation’ due to Łukasiewicz, and before long he turned his back completely on the more usual PeanoRussell notation...Formal Logic is steeped in Polish notation and the axiomatic method, and typifies Prior’s mature work.
This idea that tensed propositions are liable to be true at one time and false at another became central to Prior’s philosophy. In a summary of his views, composed nearly two decades later, he wrote: Certainly there are unchanging truths, but there are changing truths also, and it is a pity if logic ignores these, and leaves it … to comparatively informal ‘dialecticians’ to study the more ‘dynamic’ aspects of reality. (Prior 1996a: 46)
The nearest thing to a biography of Prior is:
An excellent survey of Prior's life and achievement is:
Ongoing research on the importance of Prior's philosophy and logic: