I want to consider the idea of co-referentiallity of two ideas.
Suppose Quine believes the_idea_of_Jove and the_idea_of_Jupiter mean different things.
How are we to represent this? It it itself (or rather co-referentiallity itself a primitive)?
Can we define it thus:
co-referenieal(Quine, quines_idea_of_Jove, quines_idea_of_Jupiter)
iff there is an X and
there is a meaning relation between Quine, quines_idea_of_of_Jove and X
and
there is a meaning relation between Quine, quines_idea_of_of_Jupiter and X
This does define co-referential OK.
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But Quine need not believe co-referential ideas are co-referential.
Apply the definition of belief.
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For Quine to believe quines_idea_of_Jove to be co_referential with quines_idea_of Jupiter:
There would need to be:
A belief_private of Quine’s between quines_idea_of_co-referentiallity, quines_idea_of_quines_idea_of_Jove, and quines_idea_of_quines_idea_of_Jupiter
and
Quine having a meaning relation between quines_idea_of_quines_idea_of_Jove and quines_idea_of_Jove
and also
Quine having a meaning relation between quines_idea_of_quines_idea_of_Jupiter and quines_idea_of_Jupiter
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There is no problem of intersubstitution here – (quines_idea_of_Jove and quines_idea_of_Jupiter are distinct – whether or not Jove and Jupiter are identical.)
Quine may, logically, believe the co-referentiallity of these either true or false.
Whether is belief is true depends on whether, in fact, they are co-referential.
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Also We can define Russell believes Quine believes words “Jove” and “Jupiter” are co-referential (or not).
I think one need only follow the previous definitions.