Abstract

In medieval writers we find a distinction between body as a substance – corpus-substantia – and body as a quantity – corpus-quantitas (or quantum). One of the earliest uses of this distinction is in works written by Robert Grosseteste in the 1220s. In this paper I explore his use and understanding of this distinction. I argue that he understands corpus-substantia as such as a dimensionless composite of a first corporeal form, corporeity, and prime matter. Corporeity itself is an active power for three dimensions. Through its infinite and necessary self-multiplication corporeity extends the prime matter it informs into three dimensions, thereby resulting in corpus-quantum. I explore how Grosseteste’s conception of corporeity, though probably based on ideas found in Avicenna, diverges from different understandings of Avicenna’s conception of corporeity proposed by medieval and modern commentators.