On Sense and Direct Reference
By Ben Caplan
Sense Millianism and Object Fregeanism both appeal to modes of presentation to solve one group of problems about one group of cases (namely, those that concern intuitions about the cognitive value of simple sentences, about the truth-value of some propositional-attitude ascriptions, or about sentences that contain empty names); and both appeal to objects or singular propositions to solve another group of problems about another group of cases (namely, those that concern intuitions about the truth-value of simple sentences, about the modal and epistemic profile of simple sentences, or about the truth-value of other propositional-attitude ascriptions). One further problem for both views is to explain, in a principled way, why modes of presentation matter in the first group of cases but not in the second; and, conversely, why objects or singular propositions matter in the second group of cases but not in the first. This further problem is, it seems, pressing and difficult for both views.
Source: Online Papers in Philosophy