Full Idea
Among the proposals for conditions under which two sentences have the same ordinary sense, the most liberal (Carnap and Church) is that they be logically equivalent, and the most restrictive (Benson Mates) is that they never have the same sense.
Gist of Idea
Sentences might have the same sense when logically equivalent - or never have the same sense
Source
David Kaplan (Transworld Heir Lines [1967], p.89)
Book Reference
'The Possible and the Actual', ed/tr. Loux,Michael J. [Cornell 1979], p.89
A Reaction
Personally I would move the discussion to the level of the propositions being expressed before I attempted a solution.