Shareability of thought and Frege's constraint: a reply to Onofri

Abstract

Onofri (2018) proposes an individuation criterion for thoughts that purports to satisfy both shareability (the notion that different thinkers, or a single thinker at different times, can and generally do think type-identical thoughts) and Frege's constraint (according to which two thoughts are different if it is possible for a rational subject to endorse one while rejecting the other). I argue that his proposal fails to satisfy Frege's constraint. Then I propose a modification to Onofri's proposal to fix the problem.