Chisholm’s views in ontology underwent steady pruning. In an earlier period he believed in necessarily existent states of affairs some of which might occur and recur. He also believed in times, though not in “concrete events”. Later he abandoned times and recurrable states of affairs in favor of a sparser ontology including “one shot” states, but lacking times. The earlier view can be found in “Events and Propositions” (1970), and “States of Affairs Again” (1971), and Chapter IV of [P&amp;O]. The later view appears in “Events without Times: An Essay in Ontology” (1990). See also Chapter 16 of [OM] and Chapter 10 of [RTC].