Full Idea
If you don't know what you are saying then you don't mean what you say, and also speakers generally mean what they say (in that what they say coincides with what they mean).
Gist of Idea
If you don't know what you say you can't mean it; what people say usually fits what they mean
Source
Robert C. Stalnaker (Reference and Necessity [1997], 4)
Book Reference
Stalnaker,Robert C.: 'Ways a World Might Be' [OUP 2003], p.176
A Reaction
Both these thoughts seem completely acceptable and correct, but rely on something called 'meaning' that is distinct from saying. I would express this in terms of propositions, which I take to be mental events.
Related Idea
Idea 15154 We should use cognitive states to explain representational propositions, not vice versa [Soames]