Recently, in ‘An inquiry on Fakhr al-Dīn Rāzī’s authorship of Al-manṭiq al-kabι¯r (MS Aḥmad iii, no. 3401)’, we refuted the quite common view among historians of Arabic logic as to attribute Al-manṭiq al-kabι¯r (Major [book on] logic) to Fakhr al-dīn Rāzī; however, in that paper, we could not identify the real author of the book. In this paper, we try to show that Al-manṭiq al-kabι¯r was written by Burhān al-dīn Nasafī (1203–1288), who authored another book, Sharḥ Asās al-kiyāsa whose logical (...) part is very similar to Al-manṭiq al-kabι¯r in the following significant features: the titles of chapters and sections, the style of writing, some technical as well as some non-technical terms, many sentences word by word. None of these features we find in any other Arabic logical work. So, Al-manṭiq al-kabι¯r and Sharḥ Asās al-kiyāsa are so close to each other that we might most possibly identify the authors of the books as the same scholar, i.e. Burhān al-dīn Nasafī. Fortunately, this has been verified recently by two manuscripts of a medieval Arabic logical book. (shrink)