Avicenna has been the first in the history of logic to discuss in detail the quality and the quantity of the conjunctive - conditional predicate (goz?re- h? - ye ?ari -e mottasele). He presented in simple terms the general and particular problems posed by this kind of sentence, as well as the condition of affirmation or negation. Although this analysis enabled him to precise numerous points, he didn’t give a final formal system on this subject. mainly because he mixed the common and acceptable logic of the conditional predicates, which lead to a number of contradictions. Avicenna is considered as the founder of conjuctive - conditional syllogism. Apparently, he intended to compare conditional predicates with categorical ones, and basing himself on their similarity, he used the same kind of logic for both.
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