Mohammad Ali Hodjati; Ali Reza Darabi; Lotfollah Nabavi
Volume 5, Issue 2 , September 2014, , Pages 31-53
Abstract
According to a rule in Avicenna's logic, there exists cohesion between any two necessary hypothetic propositions with identical quantity, different quality, identical antecedent, and denial of the consequent. The rule is introduced and has been argued for, by Avecinna. After him, this rule is criticized ...
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According to a rule in Avicenna's logic, there exists cohesion between any two necessary hypothetic propositions with identical quantity, different quality, identical antecedent, and denial of the consequent. The rule is introduced and has been argued for, by Avecinna. After him, this rule is criticized by Avicennian logicians. Khunaji questioned Avecinna’s pre-assumptions of this proof by examples of natural language. After Khunaji, some logicians like Nasir al-Din Tusi, Qutb al-Din al-Razi, and Qutb al-Din al-Shirazi tried to answer Khunaji’s critiques by presenting some better formalizations of Avecinna’s arguments or defending his pre-assumptions. In this paper, after introducing the arguments of both sides together with their detailed formalizations, it is concluded that the answers to Khunaji’s critiques are not enough to prove the aforementioned rule, and accepting this rule still requires new arguments.
Lotfollah Nabavi; Zinat Ayatollahi; Mohammad Saeedi Mehr; Mohsen Javadi
Volume 5, Issue 2 , September 2014, , Pages 125-145
Abstract
In traditional Aristotelian logic, the absence of a logical relation between ‘is’ and ‘ought’ statements seems to be evident, due to some characteristics of the logic. Prior relying on this fact that modern logic does not possess such characteristics, present a paradox against ...
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In traditional Aristotelian logic, the absence of a logical relation between ‘is’ and ‘ought’ statements seems to be evident, due to some characteristics of the logic. Prior relying on this fact that modern logic does not possess such characteristics, present a paradox against the advocates of the logical gap between ‘is’ and ‘ought’. In this paper, we, first, explain this paradox and a number of philosophical solutions have been proposed to solve it. Then, we illustrate and evaluate the Beall’s ‘many-valued logic’, which has been introduced as a solution to this paradox. We’ll see that this paradox could be solved in the context of the ‘relevant logic’ too. But besides of this paradox, Prior presents two other arguments, which although these two logics solve the paradox, we’ll show that each of them is unable to response to these two other arguments.