David B. Martens

In two early papers, Max Cresswell constructed two formal logics of propositional identity, pcr and fcr, which he observed to be respectively deductively equivalent to modal logics s4 and s5. Cresswell argued informally that these equivalences respectively “give . . . evidence” for the correctness of s4 and s5 as logics of broadly logical necessity. In this paper, I describe weaker propositional identity logics than pcr that accommodate core intuitions about identity and I argue that Cresswell’s informal arguments do not firmly and without epistemic circularity justify accepting s4 or s5. I also describe how to formulate standard modal logics (k, s2, and their extensions) with strict equivalence as the only modal primitive

This paper proposes a response to the duplication objection to the descriptive theory of singular mental reference. This objection involves hypothetical cases in each of which there are a pair of qualitatively indistinguishable objects and a thought that apparently refers to only one of the pair, despite the descriptive indistinguishability of the two objects. I identify a concept of reference-likeness or closeness to reference, which is related to the concept of genuine singular reference as the concept of truthlikeness or closeness to truth is related to the concept of truth. My response to the duplication objection is to say that the hypothetical cases it involves establish only that a thought can come close enough to singular reference to a thing despite not genuinely referring to that thing, a consequence that is compatible with the descriptive theory of singular mental reference.