Abul-Futuḥ Ibn-al-Ṣalaḥ Al-Ḥamadāni’s Treatise on the Fourth Figure

Abstract

Abul-Futuh Aḥmad ibn-Muḥammad ibn-al-Ṣalāḥ Al-Ḥamadāni, a logician who lived one century after Avicenna, is the first Muslim who enumerated and proved the valid and invalid moods of the Fourth Figure in his treatise: ‘On the Fourth Figure, which is attributed to Galen.’ A facsimile of this has been published in 1965, and one year later was published in USA with a fairly unsophisticated edition of Nicholas Rescher. This paper is a new edition of the treatise with many corrections and contains some new information about the history of the subject.