Abstract

In §8 of hisBegriffsschrift(1879), Gottlob Frege discusses issues related to identity. Frege begins his most famous essay,“On Sense and Denotation”(1892),published 13 years later, by criticizing the view advocated in §8. He returns to theseissues in the concluding paragraph. Controversies continue over these importantpassages. We offer an interpretation and discuss some alternatives. We defend thatin theBegriffsschrift,Frege does not hold that identity is a relation between signs.§8 of theBegriffsschriftis motivated by the conflict between two differentcriteria for sameness of conceptual content of sentences. To resolve that conflict,Frege introduces‘≡’in §8 and, thus, circumstances with names as constituents. Tothe same end, in“On Sense and Denotation,”Frege introduces senses andThoughts and abandons both ‘≡’ and circumstances. He solves what we call theCo-instantiation problem, and disregards, but does not solve, the Name problem.