Nasīr ad-Dīn al-Tūsī’s Theory of Truth; the Analysis

In developing a theory of truth, as the main condition of knowledge, four issues are usually examined: definition or analysis of truth, truth bearer, truth-maker, and relation (in correspondence and coherence theories). A proper theory of truth is the one that affords the explanation of the truth of all types of propositions, and, at the same time, resists the liar paradox. The aim of this inquiry is to analyze Nasīr al-Dīn al-Tūsī’s theory of truth one who is involved both in the liar paradox and in the explanation of the truth of the verity propositions and propositions that are made of intelligibles that have no instance in external world. This inquiry shows, with an analytical approach mostly systematic analysis, that he regards, against the difficulty of the lair paradox, propositions that are other than what they are about as the bearers of truth. Further, it shows that he, against the other difficulty, has two attitudes: first, he desists from the correspondence theory of truth and defines it as “ascription of an ideational thing to what, with its characteristic, is proper for it”; second, he considers the agent intellect to be the truth-maker. Although he regards the correspondence relation as an intentional relation, he does not discuss it much. One explanation could be that the issue of the correspondence relation does not play a serious part in the aforementioned difficulties.