As for the logic that is not mixed with philosophy, as in … the treatise of Athîraddîn al-Abharî called îsâghûjî and the works of al-Kâtibî [i.e., ash-Shamsiyya] and al-Khûnajî [Afdaladdîn (d. 1249), i.e., al-Jumal] and Sa‘daddîn [at-Taftâzânî, i.e., Tahdhîb al-Mantiq], there is no disagreement concerning the permissibility of engaging in it, and it is rejected only by he who has no inkling of the rational sciences. Indeed, it is a fard kifâya because the ability to reply to heretical views in rational theology (kalâm), which is a fard kifâya, depends on mastering this science, and that which is necessary for a religious duty is itself a religious duty.[15]