Arguments based on Leibniz's Law seem to show that there is no room for either indefinite or contingent identity. The arguments seem to prove too much, but their conclusion is hard to resist if we want to keep Leibniz's Law. We present a novel approach to this issue, based on an appropriate modification of the notion of logical consequence.

Arguments based on Leibniz's Law seem to show that there is no room for either indefinite or contingent identity. The arguments seem to prove too much, but their conclusion is hard to resist if we want to keep Leibniz's Law. We present a novel approach to this issue, based on an appropriate modification of the notion of logical consequence.

Referential opacity is the failure of substitutivity of identity (SI, for short) and in Quine’s view of existential generalization (EG, for short) as well. Quine thinks that its “solution” in epistemic and doxastic contexts, which relies on the notion of exportation, leads to undesirable results. But epistemic logicians such as Jaakko Hintikka and Wolfgang Lenzen provide another solution based on a different diagnosis: opacity is not, as in Quine’s view, due to the absence of reference, it is rather due to (...) the plurality of references; therefore, one must stabilize the reference to restore SI and EG. However, Hintikka’s semantics remains classical in its treatment of existence, which makes EG non-applicable to possible objects, while in Lenzen’s system, EG is applicable by means of a particular quantifier. But this requires adding the predicate of existence to account for real objects. In this paper, I will show the advantages and disadvantages of both solutions and will end by providing an alternative approach to the problem of non-existent objects, which stays into the frame of possible worlds semantics, but introduces some more restrictions, eliminates the problematic predicate of existence, and applies a neutral quantifier to possible non-existent objects. (shrink)

In his article “Opacity” (1986), David Kaplan propounded a counterexample to the the- sis, defended by Quine and known as Quine’s Theorem, that establishes the illegitimacy of quantifying from outside into a position not open to substitution. He ingeniously built his counterexample using Quine’s own philosophical material and novel devices, arc quotes and $entences. The present article offers detailed analysis and critical discus- sion of Kaplan’s counterexample and proposes a reasonable reformulation of Quine’s Theorem that bypasses both this counterexample and (...) another, in the author’s opinion, more persuasive counterexample, also discussed in this paper and somehow implicit in “Opacity”, which involves Russellian propositions instead of the Quinean apparatus. (shrink)