<一般論文> 大きな数としての超準数 : 超準数と厳格有限主義

Abstract

In his 2003 paper, Peacocke insisted that our implicit conception of natural numbers essentially uses a primitive recursion which consists of three clauses, and claimed that this excludes the non-standard models of natural numbers. In this article, we construct a counter “model” to his argument, which contains a non-standard natural number though the set ω of natural numbers is defined as an analogy to his primitive recursion, in a set theory with the comprehension principle within many-valued logic. This result suggests that we should interpret non-standard natural numbers from a philosophical viewpoint. We discuss this by reviewing Strict Finitism, and we conclude that non-standard natural numbers can be interpreted as “large numbers” in a Strict Finitist sense: It expresses new numbers which are introduced by expanding the notation system of natural numbers.