 The first Latin commentary on the Prior Analytics is an anonymous late twelfth-century treatise (‘Anonymus Aurelianensis III’) which involves detailed discussions of modal conversion and modal syllogisms as well as many problems dealt with in ancient commentaries. (See Ebbesen 2008; an edition by Thomsen Thörnqvist in 2015.). Dialectica Monacensis involves a brief summary of Aristotle’s modal syllogistic the elements of which were discussed in logic courses in Paris in the first part of the thirteenth century. Robert Kilwardby’s commentary Notule libri Priorum (c. 1240) became an authoritative work from which the discussions of modal syllogisms in the commentaries of Albert the Great (ca. 1250) and many others were largely derived. Abelard, who did not deal with Aristotle’s modal syllogistic, said that the modals in mixed syllogisms with both modal and assertoric premises should be understood in a way which he elsewhere characterizes as de re interpretation (Glossae super Perihermeneias XII, 189–203). This reading of modal premises was often assumed, although it was seldom discussed as such. A central problem of Aristotle’s theory is that the structure of the premises is not analyzed. Even if it is natural to think that the presupposition of the mixed moods is a de re reading of modally qualified premises, this creates difficulties when applied to the conversion rules, most of which are unproblematic only if understood as rules for modals de dicto. (According to Aristotle, necessity premises are converted in the same way as assertoric premises: ‘Every/some A is B’ implies ‘Some B is A’ and ‘No A is B’ implies ‘No B is A’. Affirmative contingency premises are converted to corresponding negative contingency premises and both these by the conversion of terms to particular contingency propositions; Prior Analytics I.3, 13.)