<一般論文>A. P. Ushenko の単純嘘つき文の議論に見る真理概念の哲学的分析の歴史

Abstract

Andrew Paul Ushenko (1900-1956) presented a version of the liar paradox that utilized a picture in 1937. He insisted that the formal logic couldn't resolve the paradox. It is important for Ushenko that logic is a part of philosophy. Although the mathematical logic was developed at that time, according to him that harms the relationship between philosophy and logic. He advocated a view of the logic, which he called "intuitionalism" that logical truth should be recognized by the logical intuition, i.e. by direct inspection without experience. Ushenko also criticized the mathematical logicians' view of the logic, and he called them "postulationalists". In 1950s, Ushenko, Encarnacion, Toms and Donnellan discussed Ushenko's liar paradox. Encarnacion and Toms pointed out Ushenko's mistakes in the proof. Toms also argued that Ushenko's liar paradox had the ambiguous reference. Donnellan interpreted this ambiguity as the difference between sentence-types and sentencetokens. Unfortunately, because of Ushenko's death, they couldn't have a discussion fully, but it is showed that sentence-types and sentence-tokens are important issues for liar paradox. It is clear from Ushenko's version of the liar paradox that the process of understanding a liar paradox doesn't need a formal language. A contextual approach to liar paradox such as Ushenko's paradox should be studied further. The findings would contribute to a system of contextual logic and philosophy of logic.