2000 年 33 巻 2 号 p. 163-175
Chapter 17 of Michael Dummett's Frege: Philosophy of Mathematics begins with the question: how did the serpent of inconsistency enter Frege's paradise? So the aim of that chapter is to explicate the primary reason for inconsistency of Frege's system (i.e. the origin of Russel's paradox). But what Dummett does in that chapter is to analyze Frege's consistency proof and to explain why his proof fails. Since it is possible that a consistency proof for a system fails but the system is still consistent, Dummett's account of inconsistency seems to be inadequate. Does Dummett succeed in explicating the origin of inconsistency of Frege's system through the analysis of his consistency proof? It is this question that this paper deals with. I shall argue that Dummett's account is inadequate and suggest an alternative explanation of inconsistency of Frege's system.