Philoponus' On Aristotle Categories 1-5 discusses the nature of universals, preserving the views of Philoponus' teacher Ammonius, as well as presenting a Neoplatonist interpretation of Aristotle's Categories. Philoponus treats universals as concepts in the human mind produced by abstracting a form or nature from the material individual in which it has its being.

The work is important for its own philosophical discussion and for the insight it sheds on its sources. For considerable portions, On Aristotle Categories 1-5 resembles the wording of an earlier...