In 1906, after giving up hope of vindicating logicism, Frege lists the results of his life's work that survive Russell's paradox. He begins:

Twenty-two years earlier, in happier times, Frege took for his third guiding principle in Die Grundlagen der Arithmetik the admonition, 'never to lose sight of the distinction between concept and object'. We cannot understand Frege's view of his epochal achievements in logic - let alone mark the distance that separates his understanding of quantificational logic from contemporary views - without an appreciation of the concept-object distinction, the centrality Frege assigns to it and its connections to his other views. The distinction embodies the quantificational understanding of generality that Frege sets against older conceptions of logic. This quantificational understanding of generality gives Frege the principle for determining the logical segmentation of sentences and the contents or thoughts expressed by sentences. I hold that Frege’s Context Principle sets forth this connection between logical segmentation and quantificational generality.

Sections 1–3 lay out Frege’s concept–object distinction and its place in his philosophy of logic. Section 4 describes Frege’s introduction of higher-level concepts and his assimilation of sentences to proper names. Sections 5 and 6 explore the charge that the concept–object distinction incoherently undermines itself in the so-called Kerry paradox. Sections 7 and 8 discuss the bearing of the Context Principle and the concept–object distinction on Frege’s logicism.