Aristotle in Plotinus’ Doctrine of Extension

This article examines the sources of Plotinus’ doctrine of extension, a central aspect of his Platonic dualism whose origins have received little scholarly attention. This doctrine entails a distinction between two central concepts: the notion of body as primarily divisible or extended ‘mass’ (ὄγκος) and that of immanent form as secondarily divisible or extended quality (ποιότης). The article argues that, although Plotinus presents this doctrine as an interpretation of Plato, Timaeus 35a, its philosophical content is irreducible to the Timaeus, and that Plotinus rather employs, adapts, and develops concepts drawn from Aristotle. First, Plotinus’ notion of ‘mass’ finds conceptual and textual parallels in Aristotle’s Physics, especially in the discussions of place and continuous magnitudes (Books IV and VI). Second, Plotinus’ distinction between bodies and qualities as primarily and secondarily divisible or extended represents a sophisticated development of chapter 6 of the Categories, where Aristotle discusses quantity and distinguishes per se and accidental quantities. Finally, the article shows that Middle Platonic authors (Ammonius Saccas, Numenius) had already employed Aristotle’s distinction between per se and accidental quantities in their anti-Stoic polemics, and that Plotinus’ engagement with Aristotle is far more sophisticated.