I was reading the article in the online Stanford Encyclopedia of Philosophy on Medieval Theories of Causation when I came along this passage:
There is, indeed, an extensive literature of medieval commentaries on the Posterior Analytics, and much of this literature is very important; we find in it a great deal of material on the authors' attitudes to necessity, the structure of science, the relation between various sciences, the autonomy of philosophy vis-à-vis theology, and the like. However, it cannot be taken to be automatically relevant to the practice of reasoning in the Middle Ages: the logical metatheory (that of the syllogism) is far too restrictive, and the conditions placed on scientific demonstrations are far too stringent, for it to be a plausible description of very many actual processes of reasoning, in the Middle Ages or at any other time.
Now, it is certainly true that most arguments in the Middle Ages are not demonstrations (they would not, I think, have claimed they were). But I'm inclined to think the logical metatheory of syllogism was not very restrictive at all, as becomes clear when one looks at examples they could give of dialectical, rhetorical, and poetic syllogisms. Most of the time we can just use the word 'deduction' or even 'inference' instead of 'syllogism', so long as we recognize that they are always thinking of it as the combination of two terms by way of a mediating term.
There's still work to be done in this aspect of medieval logic. Deborah Black here at the University of Toronto has looked at rhetoric and poetics, and the syllogisms involved, in the Islamic philosophers - al Farabi, Avicenna, Averroes (particularly Avicenna). How far similar applications of the metatheory were used by the Latins I'm not sure - the work on this is still being done (Black herself is, from what I understand, planning on a sequel to the Islamic logic book). But whether they actually applied it that way or not, it's the same metatheory, or at least, we don't currently seem to have reason to think the understanding of the syllogism was so radically different. Then again, I'm no expert in this field.
