 Ockham had claimed that it was superfluous to posit quantitative forms really distinct from substance and quality, since quantity presupposes what it is intended to explain, i.e., the extension of material substances and their having parts outside parts. As an accident, quantity presupposes substance as its substrate of inherence. Burley denies that material substances can be extended without the presence of quantitative forms, thereby affirming their necessity. He admits that the existence of any quantity always implies the existence of a substance, but he also believes that the actual existence of parts of a substance necessarily implies the presence of a quantitative form in it. He does not provide any sound metaphysical reason for this preference. But it makes sense when one considers his semantic theory, according to which reality is the interpretative pattern of (philosophical) language, so that the structure of language is a mirroring of reality. In Burley’s opinion, therefore, abstract terms in the category of quantity (such as ‘extension’, ‘duration’, ‘magnitude’, and so on) must correspond to realities in the world that are distinct from those signified by the abstract substantial terms.