 Also a minor philosophical work by a 9th-century Christian Arabic author, the Book On the Difference between Spirit and Soul (Kitab al-fasl bayna l-ruh wa-l-nafs), was translated into Hebrew in the Middle Ages (Steinschneider 1893, 289): it was quoted by some Medieval Jewish authors. Finally, in the first half of the 10th century, in the circle of al-Farabi’s followers there was an “exchange of opinions” about some metaphysical doctrines: it involved the Christian Arabic philosopher Yahya Ibn ‘Adi and two minor Jewish scholars, Ibn Abi Sa‘id al-Mawsili and Bishr ibn Sam‘an ibn ‘Irs, as shown by Shlomo Pines (Pines 1955).