Arthur Norman Prior developed tense logic. In particular, he articulated the ‘internal’ and the ‘external’ views of time, showing how both could be treated formally. Most metaphysicians think there is a ‘real’ difference between these two views, that only one describes the real nature of time. Prior too thought there is a
difference, and argued that the internal view is the ‘right’ one: that the correct view takes ‘the present’ as metaphysically privileged, and that all aspects of time could be studied from this perspective. The debate here remains heated, and today many metaphysicians support the external view, arguing that the present is not fundamentally different from other instants of time. The philosophical ramifications of this internal/external distinction need to be fully explored and our project is to explain: 1) the extent to which it drove Prior’s work, 2) what other uses the distinction might have (Prior gave us tools whose full force he himself was not always aware of).
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