Full Idea
A person who utters 'It's raining' one day does not normally make the same statement as one who utters it the next. But these variations are not accompanied by corresponding changes of meaning. The words 'It's raining' retain the same meaning throughout.
Gist of Idea
'It's raining' makes a different assertion on different occasions, but its meaning remains the same
Source
Richard Cartwright (Propositions [1962], 10)
Book Reference
Cartwright,Richard: 'Philosophical Essays' [MIT 1987], p.42
A Reaction
This is important, because it shows that a proposition is not just the mental shadow behind a sentence, or a mental shadow awaiting a sentence. Unlike a sentence, a proposition can (and possibly must) include its own context. Very interesting!