 More interesting is Burley’s solution to the problem of which entities properly fall under which categories. Unlike most medieval thinkers, he was well aware of the importance of this question, which he discusses in his middle and final commentaries on the Categories (ch. de relatione), as well as in his LsP (ch. de quando, fol. 57va). According to the common realist view, not only simple accidental forms (such as whiteness), but also the compound entities they cause when inhering in substances (a white thing—album) belong to the nine categories of accident. Burley denies this, since he regards the entities resulting from the combination of substance and accidental forms as mere aggregates: accidental beings (entia per accidens) lacking in any real unity. He claims that what is signified by abstract terms, i.e., simple forms such as whiteness and fatherhood, properly falls under the categories, whereas what is signified by concrete accidental terms does not. An aggregate may be said to belong, improperly and reductively, to the category to which its accidental form belongs (Tsp, ch. de relatione, ed. Conti, pp. 60–61; EP, chs. de relatione fol. 35va, and de qualitate, fol. 41rb). Concrete substance-terms (such as ‘man’) are different, however. For even though they signify composites, they signify beings with a real, per se unity that properly belongs to the category of substance. In this case, the abstract forms connoted by concrete substance terms (e.g., the form of humanity by ‘man’) do not lie outside the nature of the things themselves, i.e., the individual substances for which the concrete substance-terms supposit. Thus, both the form and its substance belong to the same categorial field (EP, ch. de denominativis, fol. 19va–b). In this case, the individual substances are the bearers (supposita) of the form and not its subject (subiecta), as they are instantiations of it and not mere vessels of inherence (TdU, p. 58; see also De relativis, p. 168).