Book excerpt: This Element provides an overview of how the ancient thinkers theorised about properties; such overview puts in relief the inquiries, problems and solutions they (Anaxagoras, Plato and Aristotle) were pursuing, while engaged in dialogue with each other. It examines alternative philosophical perspectives existing in antiquity concerning the explanation of property qualification, qualitative similarity, compositeness, and oneness. It further argues that it was Plato who first conceptualised recurring universals but did not reify them and did not admit them in his ontology; it was Aristotle who did, and developed his metaphysics around them. It concludes by showing that Aristotle, building on Plato's work, identified the metaphysical phenomenon of the instantiation of properties and developed an account for it. Finally, the Element outlines Aristotle's 'sophisticated' account of the oneness of a substance and argues that it was not hylomorphic.