  The two Peripatetics seem to have redefined Aristotle’s first figure, so that it includes every syllogism in which the middle term is subject of one premise and predicate of the other. In this way, five types of non-modal syllogisms only intimated by Aristotle later in his Prior Analytics (Baralipton, Celantes, Dabitis, Fapesmo and Frisesomorum) are included, but Aristotle’s criterion that first figure syllogisms are evident is given up (Theophrastus fr. 91, Fortenbaugh). Theophrastus and Eudemus also improved Aristotle’s modal theory. Theophrastus replaced Aristotle’s two-sided contingency with  one-sided possibility, so that possibility no longer entails non-necessity. Both recognized that the problematic universal negative (‘A possibly holds of no B’) is simply convertible (Theophrastus fr. 102A Fortenbaugh). Moreover, they introduced the principle that in mixed modal syllogisms the conclusion always has the same modal character as the weaker of the premises (Theophrastus frs. 106 and 107 Fortenbaugh), where possibility is weaker than actuality, and actuality than necessity. In this way Aristotle’s modal syllogistic is notably simplified and many unsatisfactory theses, like the one mentioned above (that from ‘Necessarily AaB’ and ‘BaC’ one can infer ‘Necessarily AaC’) disappear.