Full Idea
No one says or thinks anything ambiguous, and nothing should be held to be being said beyond what the speaker thinks he is saying.
Gist of Idea
Thought is unambiguous, and you should stick to what the speaker thinks they are saying
Source
report of Diodorus Cronus (fragments/reports [c.300 BCE]) by Aulus Gellius - Noctes Atticae 11.12.2
Book Reference
'The Hellenistic Philosophers:Vol.1 translations', ed/tr. Long,A. /Sedley,D. [CUP 1987], p.227
A Reaction
A key argument in favour of propositions, implied in this remark, is that propositions are never ambiguous, though the sentences expressing them may be