 Kamp explains these facts in the following way. The imparfait does not introduce its own reference time and in (60a) there is no previous reference point given. Therefore (60a) is out. In (60b) the sentence in the passé simple Jean ôta sa veste introduces a reference time that can be used to anchor If faisait chaud. The imperfective aspect of the imparfait is then explained by the fact that the PS event happens while the sentence in the imparfait holds. Thus passé simple and imparfait not only provide temporal information but they also serve as means to structure discourse in different ways.