Logic and Reality: Essays on the Legacy of Arthur Prior

Logic and Reality: Essays on the Legacy of Arthur Prior

Logic and Reality: Essays on the Legacy of Arthur Prior

Logic and Reality: Essays on the Legacy of Arthur Prior


Logic and Reality is a collection of essays by philosophers, logicians, mathematicians, and computer scientists, celebrating the work of the late distinguished philosopher Arthur Prior on the eightieth anniversary of his birth. Topics range from philosophical discussions of the nature of time and of the nature of logic itself, to descriptions of computer systems that can reason and take account of the fact that they exist in a temporal world.


Prior's most remarkable achievement was the establishment of the calculus of past, present, and future. This was not only a matter of formalism. Prior regarded the issue of tense as strongly related to basic questions in ontology. It seems fair to call Prior's ontological position temporal realism. His central ontological tenet was that the distinction between past, present, and future is real. This position is an alternative to what he called the tapestry view of time, according to which time as a whole is there all at once. Prior pointed out that some (but not all) medieval theologians held this tapestry view of time and that nowadays many philosophers of science claim that the Special Theory of Relativity supports this view of time.

The following two texts by Prior, 'A Statement of Temporal Realism' (hereafter TR) and 'Some Free Thinking about Time' (hereafter SFTT), clearly illustrate what he meant by temporal realism, why he was in favour of this view, and why he rejected the tapestry view of time.

The two pieces are kept at the Bodleian Library in Oxford. They are not dated, but since in a note on the typescript of TR Prior describes himself as the 'author of Past, Present and Future', he must have written this paper sometime during the last years of his life. It is much more difficult to date SFTT. There is a certain textual overlap with the paper 'The Syntax of Time-Distinctions' (hereafter STD), which was published in 1958 and was based on the Presidential Address that Prior gave to the New Zealand Congress of Philosophy in Wellington on 27 August 1954. SFTT appears to have been prepared for oral presentation (whereas STD is written for publication in a philosophical journal), so it is possible that SFTT formed part of Prior's text for the Wellington address. However, there are also important differences between SFTT and STD, especially concerning the treatment of relativity. STD seems less mature than SFTT in this respect. In STD Prior remarked that relativity is often based on what he called an l-calculus (i.e. a calculus of earlier and later):

At least in many of its presentations, relativity theory seems to be as closely bound up with the 'spread-out-eternally' view of time underlying the l-calculus as medieval theology was. On this, one possible comment is that this may be simply a philosophical defect . . .

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