Full Idea
Montague's intensional logic was the first really successful attempt to develop a mathematical framework that incorporates the notion of meaning.
Gist of Idea
Montague's intensional logic incorporated the notion of meaning
Source
Keith Devlin (Goodbye Descartes [1997], Ch. 8)
Book Reference
Devlin,Keith: 'Goodbye Descartes: the end of logic' [Wiley 1997], p.192
A Reaction
Previous logics, led by Tarski, had flourished by sharply dividing meaning from syntax, and concentrating on the latter.