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• Marco Ruffino　　“Why Frege would not be a neo-Fregean”,　in: Mind, New Series, vol. 112, no. 445, 2003

In this paper, I seek to clarify an aspect of Frege's thought that has been only insufficiently explained in the literature, namely, his notion of logical objects. I adduce some elements of Frege's philosophy that elucidate why he saw extensions as natural candidates for paradigmatic cases of logical objects. Moreover, I argue (against the suggestion of some contemporary scholars, in particular, Wright and Boolos) that Frege could not have taken Hume's Principle instead of Axiom V as a fundamental law of arithmetic. This would be inconsistent with his views on logical objects. Finally, I shall argue that there is a connection between Frege's view on this topic and the famous thesis first formulated in ‘Uber Begriff und Gegenstand’ that ‘the concept horse is not a concept’. As far as I know, no due attention has been given to this connection in the scholarly literature so far.

• 井上直昭　　「論理的対象とは何であるか」、『筑波哲学』、第11号、2001年
• 中戸川孝治　　「トポス理論へ向けて: 哲学的考察(1)」、『筑波哲学』、第7号、1996年

Ruffino論文と同種のテーマを扱った論文に

• 野本和幸　　“Why, in 1902, wasn't Frege prepared to accept Hume's Principle as the Primitive Law for his Logicist Program?”,　in: Annals of the Japan Association for Philosophy of Science, vol. 9, no. 5, 2000

というのがある。こちらは既に以前に入手済みなのでRuffino論文と合わせて読もうかな。

井上論文はNeo-Fregean Logicismの話である。