• Korean Journal of Logic
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• v.18 no.3
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• pp.307-335
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• 2015

An important component in Prawitz's and Dummett's proof-theoretic accounts of validity is the condition for validity of open arguments. According to their accounts, roughly, an open argument is valid if there is an effective method for transforming valid arguments for its premises into a valid argument for its conclusion. Although their conditions look similar to the proof condition for implication in the BHK explanation, their conditions differ from the BHK account in an important respect. If the premises of an open argument are undecidable in an appropriate sense, then that argument is trivially valid according to Prawitz's and Dummett's definitions. I call this 'the triviality problem'. After a brief exposition of their accounts of proof-theoretic validity, I discuss triviality problems raised by undecidable atomic sentences and by Godel sentence. On this basis, I suggest an emendation of Prawitz's definition of validity of argument.

• Korean Journal of Logic
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• v.16 no.3
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• pp.407-436
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• 2013

I examine the notion of truth in the intuitionistic type theory and provide a better explanation of the objective intuitionistic conception of mathematical truth than that of Dag Prawitz. After a brief explanation of the distinction among proposition, type and judgement in comparison with Frege's theory of judgement, I examine the judgements of the form 'A true' in the intuitionistic type theory and explain how the determinacy of the existence of proofs can be understood intuitionistically. I also examine how the existential judgements of the form 'Pf(A) exists' should be understood. In particular, I diagnose the reason why such existential judgements do not have propositional contents. I criticize an understanding of the existential judgements as elliptical judgements. I argue that, at least in two respects, the notion of truth explained in this paper is a more advanced version of the objective intuitionistic conception of mathematical truth than that provided by Prawitz. I briefly consider a subjectivist's objection to the conception of truth explained in this paper and provide an answer to it.

• Electronics and Telecommunications Trends
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• v.11 no.3 s.41
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• pp.71-84
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• 1996

Girard에 의해서 1987년에 처음 소개된 선형 논리(linear logic)는 컴퓨터 사이언스에 큰 관심을 불러 일으키며 빠르게 발전하고 있다. 선형 논리는 상태 및 자원을 논리적 수준에서 다루고 있는 특징이 있다. 본 고에서는 선형 논리의 의미, 동기 및 특성을 소개하며, Gentzen의 시퀀트 계산법과 Prawitz의 자연 연역법 사이의 연관성 및 여러 증명 사이의 '같음'에 대한 개념을 컷제거 정리 측면에서 논의하고, 이러한 개념에 의하여 선형 논리의 증명이 증명망으로서 표현될 수 있음을 보인다.