Full Idea
Three periods can be distinguished in philosophical logic: the syntactic stage, from Russell's definite descriptions to the 1950s, the dominance of possible world semantics from the 50s to 80s, and a current widening of the subject.
Gist of Idea
Three stages of philosophical logic: syntactic (1905-55), possible worlds (1963-85), widening (1990-)
Source
Horsten,L/Pettigrew,R (Mathematical Methods in Philosophy [2014], 1)
Book Reference
'Bloomsbury Companion to Philosophical Logic', ed/tr. Horsten,L/Pettigrew,R [Bloomsbury 2014], p.15
A Reaction
[compressed] I've read elsewhere that the arrival of Tarski's account of truth in 1933, taking things beyond the syntactic, was also a landmark.