 There is almost no mention of modal syllogisms in any of al-Fārābī’s surviving works. He must have discussed modal syllogisms in his [Commentary on Prior Analytics]; but the relevant part of this work is lost and we have to rely on citations by Avicenna, Averroes, and Maimonides. These citations between them tell us of only one modal syllogistic mood that al-Fārābī either accepted or  rejected.[15]