Born in Qazvin, Najm al-Dīn al-Kātibī (b. 600/1204) was a Persian philosopher and scholar who was a member of the Shāfiʿī school of law. His most famous work aside from The Rules of Logic is Philosophy of the Source, a text about physics and metaphysics. Tony Street is Assistant Director of Research in Islamic Studies at the University of Cambridge’s Faculty of Divinity and is a Fellow of Clare Hall.