Conceptual and judgmental foundations of a widespread controversy on validity of conditional syllogism

In his logical book, al-Qiyas al-Shifa, Avicenna proposed his theory on conditional syllogism and then posed a doubt on the validity of conditional Barbara by a seemingly counter-example with minor premise which has an impossible antecedent. He and his followers proposed at least five different answers: 1. falsity of the minor of the counter-example, 2. falsity of the major, 3. truth of the conclusion, 4. failure of repetition of middle term, and 5. invalidity of conditional Barbara. In this paper, we show that these five reactions are rooted in ambiguities in the meaning of “cogent conditional;” and to withdraw the ambiguities, it is needed to answer important questions. By the aid of these answers, we can achieve Sinavi logicians’ conceptual and judgmental foundations for conditional syllogism