  In December 1965 Scott delivered his famous talk to the Hume Society at Stanford entitled ‘The Logic of Tenses’. A multilith of Scott’s handwritten notes for this talk has been circulating ever since among tense logicians. Four days later Prior himself addressed the Society, again on tense logic. It was in this fecund atmosphere that Prior completed the manuscript of his book Past, Present and Future, which remains to this day one of the most important references in the field.