 Crucially, topical arguments were originally seen as merely probable, contrasting with the necessary truth-preservation of syllogisms. So for maximal propositions to serve as grounds for the relation of consequence, a transformation on the status of topical arguments (from probable to necessary) had to occur at a later stage (Stump 1982, 290). Moreover, it is important to notice that, although Boethius is familiar with the work of the Greek ancient commentators and incorporates some elements from their discussions, he does not explicitly apply the form vs. matter distinction to syllogisms, as the earlier authors had done. Barnes (1990) suggests that the logical hylomorphism (i.e. the application of Aristotle’s doctrine of form and matter to logic) of these authors is nevertheless present in Boethius’ terminology, such as in the opposition between propositionum complexio and rerum natura (the structure of a sentence vs. the nature of things) (e.g. HS II ii 5). But Boethius does not present the idea of substitution/variation of terms as a property related to the validity of arguments, as Alexander of Aphrodisias had suggested. In other words, substitutivity of terms as captured by (ST) is not a key element of Boethius’ account of validity — neither terminologically nor conceptually.