 In the thirteenth and fourteenth centuries, all the realist authors, with the only notable exception of Duns Scotus, regarded categorial items as composed of two main aspects: the inner nature or essence, and their peculiar mode of being or of being predicated (modi essendi vel praedicandi). They maintained that the categorial table divides categorial items according to their modes of being (or of being predicated) and not according to their inner natures (or essences). In particular, Thomas Aquinas (Sententia super Metaphysicam, liber V, lectio 9) based his method of finding the ten Aristotelian categories on the differences of modes of being predicated, and recognized three fundamental modes of being predicated: essentially, proper to substances, when the predication indicates what a given thing is; accidentally, proper to quantities, qualities, and relatives, when the predication indicates that something inheres in a subject; and externally, proper to the remaining six categories, when the predication indicates that something which does not inhere in the subject nevertheless affects it. On the contrary Albert the Great (Liber de praedicamentis, tr. I, cap. 7) and Simon of Faversham (Quaestiones super librum Praedicamentorum, q. 12) based their method of finding the categories on the differences of modes of being. They admitted two fundamental modes of being: being by itself, proper to substance; and being in something else, proper to the nine genera of accidents. The latter was subdivided into being in something else absolutely, proper to quantities and qualities, and being in something else in virtue of a relation to a third thing (esse ad aliud), proper to the remaining seven categories. Walter Burley, whose last commentary on the Categories is, along with Wyclif’s De ente praedicamentali, the main source of Alyngton’s commentary on the Categories, recalled two ways of deducing the ten Aristotelian categories, both based on the various levels of similarity among their own modes of being. Alyngton follows very closely Burley’s first way of deriving the ten categories. In his opinion, there are two fundamental modes of being proper to things: being by itself, which characterizes substances, and being or inhering in something else, which characterizes accidents. The latter is subdivided into three less general modes: being in something else in virtue of its matter; being in something else in virtue of its form; and being in something else in virtue of the whole composite. Something can inhere in something else in virtue of its matter, form, and composite according to three different ways: from inside (ab intrinseco), from outside (ab extrinseco), and partially from inside and partially from outside (partim ab intrinseco et partim ab extrinseco). If something is in something else in virtue of its matter and from inside, then it is a quantity; if from outside, it is a where; if partially from inside and partially from outside, it is an affection. If something is in something else in virtue of its form and from inside, then it is a quality; if from outside, it is when (quando vel quandalitas); if partially from inside and partially from outside, it is an action. If something is in something else in virtue of the whole composite and from inside, then it is a relation; if from outside, it is a possession (habitus); if partially from inside and partially from outside, it is a position (In Cat., cap. de numero et sufficientia praedicamentorum, pp. 252–53).