مجله معارف منطقی
پیاپی 1 (پاییز و زمستان 1393)

Logic is a science that studies the methodology of thinking (reasoning). Thinking can be defined as the process through which one can move in an orderly way from previously established knowledge (the known) to new knowledge or to what is commonly called the unknown (conclusion). Previously established knowledge and the way it is organized and arranged [in the mind] is the perfect cause in relation to what can be properly called the induction of a conclusion in the process of thinking. That is why all the principles and rules governing cause and effect can also be applied to "previously established knowledge" as cause and to subsequent new knowledge as effect (conclusion and definiens). Such a view of previously established knowledge and conclusion can result in certain subtle points in the science of logic. Other issues and divisions in logic and their relevant rules and principles are based on the view mentioned above. Demonstration, as a logical category, is among the topics whose content explanation has a direct relation to knowing what causes a judgment and what are its various types. Lack of a careful study of the etymology of cause, particularly the cause of a judgment and making no distinction between logical and philosophical attitudes and aspects when discussing about demonstration have led to ambiguity in some propositions, giving rise to certain unscientific accounts. In this article, the author tries to deal with the etymology of cause, the distinction between logical and philosophical approaches to it and their implications and consequences, types of causes of a judgment and conditions of a cause for forming a demonstration. The explanation and assessment of Khawja's opinion concerning the application of four causes in a priori demonstration constitute the main discussion in this article.

The question of possibility of knowing God is a fundamental issue in theology. This question can be scrutinized in these two fields: the 'possibility of conceptual knowledge' and the 'possibility of assertive or propositional \ knowledge'. According to the Muslim and Western theologians’ current opinions, it is possible to have conceptual and assertive knowledge about God. There are, however, scholars who have challenged the possibility of knowing God. The most important challenges for the possibility of having a conceptual knowledge about God are as follows: 1. Sense data (sensualism) theories in the treatment of conceptions in epistemology 2. Logical positivism 3. The question of something being conceivable while having an essence. 4. Conceivability and anthropomorphism 5. Conceivability and the limitation of man's perception faculties. The advocates of this theory have resorted to some traditions as well. This theory has emerged as a result of the occurrence of some mistakes in some epistemological principles and the confusion between essential and philosophical concepts as well as making no distinction between the principles applicable to both a concept and its (external) instances. The most important challenges of the theory of having assertive or propositional knowledge about God are as follows: 1. Basing arguments on empirical theories in treating assertive knowledge in epistemology,2. The possibility of proving God through demonstration and the commonality between definition and demonstration.3. The possibility of proving God through demonstration and the impossibility of a priori demonstration.4. The possibility of proving God through demonstration and a posteriori demonstration. This theory has also appeared as a result of some mistakes in epistemology or logical principles.

The question of commonality between definition and demonstration is among the issues considered in logic. Mullā Ñadrā has dealt with it while treating such concepts as Absolute Being, the existence of God and the Real One. According to some scholars, the commonality is persistent; namely every definition has a demonstration and every demonstration has a definition. Definition and demonstration cannot be deduced from each other. They are different things. The only place where definition and demonstration converge is the affirmative a priori demonstration composed of essential causes. Thus, Mullā Ñadrā and other philosophers’ contention that whatever does not have a definition does not have a demonstration, for definition and demonstration have the same limits, can be reduced to whatever does not have a definition does not have an affirmative a priori demonstration composed of essential causes. This is because only definition and an affirmative a priori demonstration made of essential four causes share the same limits.

The present article is intended to reflect on Muslim logician's views concerning what is called ‘resistance syllogism’ in their philosophical jargons. Resistance syllogism is, by definition, a kind of argument that can falsify the strongest premise in an argument for a theory. Though it was originally presented by Aristotle, it was developed, though with some ups and downs, by Muslim logicians in the Islamic era. Resistance syllogism being taken as a methodology for criticism has occupied a high status in some logical books as Muslim thinkers give importance to the question of criticism. The main aim of the present study is to lay emphasis on this point that Muslim thinkers have paid considerable attention to many of the issues related to methodology [of criticism], though these issues did not assume the form of an independent work and remained instead scattered in logical works. The present article is a case-study with an historical approach, aiming at illustrating how Muslim logicians conceptualized the so-called resistance syllogism. It also gives an analysis of its methodological place as an example of the methodological issues treated by the early Muslim logicians. Through rethinking and reconsidering Muslim thinkers’ thoughts and opinions in the realm of Islamic cultural tradition, one can reconstruct and reproduce the very model they have perused in their scientific studies.

In modern times, comparative discussions of the ideas of ancient and modern logicians constitute an important branch of logic. At the zenith of such discussions lies the comparison between material implication in modern logic with the concept of a conditional in ancient logic. After briefly studying theconcept of material implication and the reason why contemporary logicians tend to interpret conditional propositions in ancient logic as material implication, this article makes a critical assessment of the opinions expressed by some contemporary logicians in this connection. The present study presents the arguments offered by those supporting the convergence of these two forms of logic and immediately makes them subject to a critical assessment. This writing is mainly focused on the discussion raised about the two controversial theories presented by MurtaÃā Hājj Husaini and Asadullāh Fallāhi. Having confirmed Fallāhi's theory, the writer seeks to show that, though previous logicians were always considering the concept of material implication as a presupposition, they did not clearly speak about it. Thus the attempts made to reconcile between the two systems of logic never produced expected results nor did they prove that material implication formed the basis of logical deductions in ancient logic.

Some contemporary logicians have formulated factual and external propositions as being a conjunction and a conditional respectively in the scope of a quantifier, which makes many rules of ancient logic invalid. The present study aims to show that if, according to the analysis of the contemporary logicians, the conjunctive and the conditional which appear in the scope of a quantifier are placed before a quantifier (that is if we bound new formulae in modern logic to their subjects through a conjunctive or a conditional) most rules of ancient logic will hold for all external propositions though they will not hold in most cases for factual propositions. Based on this formulation, to restrict the rules of ancient logic to external propositions will become extremely significant. Though not claiming to be in full compliance with the mind set of great Avicennian logicians, this new formulation of factual and external propositions is somewhat in harmony with the rules of ancient logic and is faced with fewer problems compared to the formulation of some contemporary logicians.

The only way to overcome the complications of understanding Khunji's ‘reverse contradiction’ is to understand his ‘permanently true non-modal propositions’. His permanently true non-modal propositions are so mixed up with his ‘reverse contradiction’ that understanding the former can be said to be tantamount to understanding half of the latter. In order to promote the invaluable discussions of ancient logic, especially the discussions that have appeared in Khunji's Kashf al-Asrār, this article deals with Khunji's ‘permanently true propositions’. The propositions that are permanently true, according to Khunji, are not as such in modern logic and this bring evidence for the fact that either the formulation of these propositions are flawed or there is a difference between Khunji's logic and modern logic. This article shows that the formulation of this proposition in modern logic is flawed and that Khunji has made use of axioms that are not used in modern logic.