 It will become clear that Avicenna's syllogistic puzzled those who came after him, and still puzzles those today who try to work out what Avicenna was doing. There is some ground to think that Avicenna's syllogistic is, from a systematic point of view, something of a failure; that was a fairly common assessment among thirteenth-century logicians. This in turn gives rise to the thought that perhaps Avicenna wasn't trying to produce a systematic syllogistic, that he had other goals in mind as he dealt with material descended ultimately from Aristotle's Prior Analytics (some of it, from the commentators, seemingly in conflict with what Aristotle is doing). If I understand correctly, this is broadly speaking how Hodges approaches Avicenna (see Hodges 2011b, 2012a, and 2012b in  Other Internet Resources). On the other hand, it may be that Avicenna has a complex system that repays close analysis; Thom's studies of Avicenna's syllogistic proceed on that assumption. I tend to think the Thom approach is the more promising. In any event, thirteenth-century logicians took Avicenna to have tried and failed to present a coherent system.