物理主義的真理論とは何か―フィールドのタルスキ批判をめぐって―

Abstract

Alfred Tarski says that his definition of truth is in harmony with the postulates of physicalism. What Tarski means by 'physicalism, ' however, has not been understood well. In this paper the author tries to make it clear what Tarski's physicalism in semantics is. First, the author examines Hartry Field's well-known article 'Tarski's Theory of Truth, ' in which he contends that although Tarski's philosophical purpose in the theory of truth is to pursue physicalism, Tarski fails to do so. There Field suggests his understanding of physicalism as the basis of his contention. According to Field, physicalistic semantics ought to explain the causal connection between language and (extralinguistic) reality. Such an explanation demanded by Field is something which one may naturally expect from physicalistic semantics. But the problem is : Is it also what Tarski demands of physicalistic semantics ? Second, in order to solve the problem, the author investigates Tarski's two methods of introducing the concept of truth, namely, the method of definition and the axiomatic method. Tarski regards the former as physicalistic, the latter non-physicalistic. When this distinction is made, whether or not a method can explain the causal connection between language and reality is not used as the criterion by Tarski. According to Tarski, that a method does not contain any special theories of truth is the criterion for the method to be physicalistic. Accordingly, the axiomatic method is judged non-physicalistic because it characterizes the properties of the concept of truth by its own special axioms. From the physicalistic point of view, the concept of truth does not need to be explained at all, but only to be defined. This is Tarski's physicalistic theory of truth. Therefore the author concludes that Field's physicalism is not the same as Tarski's and that Tarski succeeds in pursuing his own version of physicalism.