Full Idea
Perhaps it is impossible that an event should have had a causal history different from the one that it actually had.
Gist of Idea
Maybe each event has only one possible causal history
Source
Jonathan Bennett (Event Causation: counterfactual analysis [1987], p.220)
Book Reference
'Causation', ed/tr. Sosa,E. /Tooley,M. [OUP 1993], p.220
A Reaction
[He cites van Inwagen for this] The idea is analagous to baptismal accounts of reference. Individuate an event by its history. It might depend (as Davidson implies) on how you describe the event.