The refutation of the three Christian sects
Original Language: Arabic
It was presumably a summary of the longer version of the Radd. The work has not survived, and is only known from Ibn al-Nadīm's list (Fihrist, p. 216) where it is referred to as Kitāb al-radd ʽalā l-Naṣārā l-awsaṭ, 'The refutation of the Christians, medium version'.
There is a slim possibility that traces of it are to be seen…