MANTEQ-PAZHUHI (LOGICAL STUDIES)
Year:2019 | Volume:9 | Issue:2 |Papers Count:6

The purpose of this research is to provide a new concept in Aristotelian categorical syllogism which is called groundability. A valid mood is called groundable if one would derive all the 24 valid moods in the Aristotelian’ s syllogism by assuming only the valid mood and applying a chain of the following rules: simple conversion, reduction-ad-absurdum, sub-alternation, obversion and quantification negation. In this paper, we will prove that only the fifteen valid moods have the groundability property. Because Aristotle proves all the valid moods of other figures based on the four moods in the first figure, he considers these moods of the first figure as moods having the groundability property. We show that the groundability is not restricted to the first valid moods of the first figure--they are fifteen moods as stated. Thus, it can be shown that Aristotle's purpose from the self-evidence of the first figure is not the groundability of the four moods in the first figure. This important logical result in Aristotle's system is gained through the introducing the concept of the groundability of the moods in syllogism. We show that unlike the common view in the Aristotelian tradition, it is not the case that the groundability of the first figure must be the basis for explaining of being self-evidence of the four moods of the first figure. Regardless of what lies behind the evidence of the first figure valid moods, this paper will eliminate one of the options which is somehow a common wrong interpretation for answering the problem

Relation and logical analysis of its features and rules of inference were one of the logical concerns of Muslim logicians; though each one has different approaches. Not considering the distinction between propositions containing relations and propositions containing categorical concepts has caused some inconsistency in their logical text; that is although Aristotelian logic focuses only on subject-predicate structure of sentences and has not a separate analysis for relations, however, obviously its importance were not neglected. So the inferential rules of relations has not developed in Aristotelian logic due to this inconsistency and it is not easy to capture the Muslim logician`s idea about it. Nevertheless this thread of thought could be found in analysis of Four-fold Relations, conversion of universal negative propositions, the first figure of syllogism, Equality Syllogism and essential and non-essential middle term.

In this paper I evaluate Geirsson’ s justification model for modal beliefs which he proposes in “ Conceivability and Defeasible Modal Justification” (2005). Geirsson’ s justification model is based on conceivability. Geirsson gives an analysis of conceivability in terms of imagination. Geirsson admits that his account is similar to Yablo’ s model, but he claims that it advances discussion in several ways. One of the claimed improvements is to employ propositional imagination for justification of modal beliefs. In this paper I will argue that Geirsson’ claimed advancements are not very useful. For among other things propositional imagination as he defines it could not provide justification for modal beliefs. Moreover Geirsson could not give an answer to the question “ what exactly is propositional imagination? ” based on which what he considers propositionally imaginable, e. g. denial of Goldbach's conjecture, would still be imaginable but metaphysically impossible propositions would not be propositionally imaginable.

The main Frege’ s question in “ On sense and reference” is that how we can understand the difference between cognitive value of a=a and a=b? “ a=a” is analytic and a priori while “ a=b” is a posteriori and has different cognitive value. Frege’ s theory of sense and reference wants to answer to this question. Sense is mode of presentation of the reference. The difference between modes of presentation of reference can be a good reason for cognitive value of empirical identities. In analytic philosophy, this response is considered as some strength of Frege’ s theory. We are going to argue that if we accept the suggested logical form by Frege and his theory of sense and reference, then empirical discovery is vanished. We ascribe other logical form to Frege’ s intended sentences and this form displays the requirement for empirical discovery and it does not need to resort to his theory of sense and reference.

There are three theories regarding the quality of ascription of essential on essence and on each other. Most logicians consider that ascription of genus and differentia on the genre and on each other is common technical predication. But according to Allameh Tabatabai, the genus is the same as the ambiguous genre and the differentia is the same the determined genre and the genre is the complete essence without ambiguity and actuality. Contrary to popularity, therefore, he considers ascription of genus and differentia on the genre is primary essential predication but ascription of genus and differentia on each other is common technical predication. But Ayatollah Javadi Amoli, one step ahead of Allameh Tabatabaee, considers that ascription of genus and differentia on the genre and on each other is primary essential predication. In this article, while explaining all three perspectives, we first criticize them and finally we conclude that the famous theory is correct.

Complex demonstratives are linguistic expressions of the form "that F", that result from combining demonstrative pronouns with simple or complex common noun phrases. There are two well-known theories about the semantic behavior of complex demonstratives: the first is the direct reference theory and the second is the quantificational theory. According to direct reference theory, complex demonstratives are referring terms and their contents, in demonstrative use, are individuals, and 'f' contributes to fixing the referent of "that F" but contributes nothing to the semantic content of the containing sentence. By contrast, quantificational theory treats complex demonstratives as quantifier phrases, and holds that a two-place relation between properties is contributed to the proposition expressed by the sentence containing the complex demonstrative. This theory claims to account for all sorts of uses of complex demonstratives, such as, demonstrative, NDNS, QI, bound-variable and anaphoric, which have been used by the defenders of this theory to pose objections to the direct reference theory. Yet, direct reference theorists not only can reply to these objections, but also present problems involving given uses in modal contexts and other contexts against quantificational theory, that such contexts can raise serious difficulties for quantificational theory. Altogether, it seems the direct reference theory presents more intuitive explanation about the complex demonstratives