Summary: This paper deals with the relationship between material substrate and its individuating quality. According to Stoic metaphysics, it is matter that qualifies matter; and therefore there is no entity or cause other than body-matter itself which makes an individual into a ‘peculiarly qualified individual’. Πνεῦμα is a key-concept in this issue since both
passive matter (substance) and active matter (quality) are but its ‘dispositions’. Quality, πνεῦμα and λόγος σπερματικός are related to each other and must be taken into account for bodies which have the highest degree of unity: the organic entities. Inorganic entities and artefacts may just be considered ποία. Only organic entities are ἰδίως ποιά.