 As laid out above, Prior’s invention of tense logic was largely motivated by the use of tense in natural language. An alternative early logical approach to tense was provided by Reichenbach (1947), who suggested an analysis of the English verbal tenses in terms of three points in time: speech time, event time, and reference time, where the reference time is a contextually salient point in time, which, intuitively, captures the perspective from which the event is viewed. Using the notion of reference time, Reichenbach was able to distinguish, for example, between the simple past (“I wrote a letter”) and the present perfect (“I have written a letter”), which are conflated in Prior’s account. In both cases, of simple past and of present perfect, the event time precedes the speech time; but, in the former case the reference time coincides with the event time whereas in the latter case the reference time is simultaneous with the speech time.