Full Idea
If the sense of a name was subjective, then the proposition and the thought would be subjective; the thought one man connects with this proposition would be different from that of another man. One man could not then contradict another.
Gist of Idea
Senses can't be subjective, because propositions would be private, and disagreement impossible
Source
Gottlob Frege (Letters to Jourdain [1910], p.44)
Book Reference
'Meaning and Reference', ed/tr. Moore,A.W. [OUP 1993], p.44
A Reaction
This is an implicit argument for the identity of 'proposition' and 'thought'. This argument resembles Plato's argument for universals (Idea 223). See also Kant on existence as a predicate (Idea 4475). But people do misunderstand one another.
Related Ideas
Idea 223 If you deny that each thing always stays the same, you destroy the possibility of discussion [Plato]
Idea 4475 Saying a thing 'is' adds nothing to it - otherwise if my concept exists, it isn't the same as my concept [Kant]