As such there is the issue of what is involved in attributing to a speaker implicit knowledge of such a theory. Frege's first argument for the distinction between sense and reference has two premises. The first is that all theoretical knowledge is propositional knowledge. That is all predicative knowledge rests on some bit of propositional knowledge. The second is, for any given piece of predicative knowledge there will never be a unique proposition the knowledge of which would imply possession of that piece of predicative knowledge.
Predicative knowledge is a more restricted form of knowledge than propositional knowledge.
The knowledge which the subject has can always be further characterised by citing the propositional knowledge on which the predicative knowledge rests. When citing the propositional knowledge of the subject one will display the sense which the speaker attaches to the word in the case of knowledge of the reference of the word. Dummett then mounts a defence against some one who rejects the second premise, the most likely point of attack. Someone with a sufficient grasp of grammar could recognise that 'Valencia' is a proper name, that proper names have references, that, as a proper name, 'Valencia' will refer to whatever thing Valencia is and still not have any idea what that thing is. The conflation that Dummett claims is between talk that goes no further than the boundaries of language and talk that does go beyond the boundaries of language.