Full Idea
Determinism is the proposition that, for every event that occurs, there occurs a sufficient causal condition of that event.
Gist of Idea
Determinism claims that every event has a sufficient causal pre-condition
Source
Roderick Chisholm (Person and Object [1976], 2.2)
Book Reference
Chisholm,Roderick: 'Person and Object' [Open Court 1976], p.59
A Reaction
You need an ontology of events to put it precisely this way. Doesn't it also work the other way: that there is an event for every sufficient causal condition? The beginning and the end of reality pose problems.