YUHANNA IBN SAWIRUS
The author of a single work, Kitab al-‘Ilm wa-al-‘Amal (Book of Theory and Practice). The oldest manuscript dates from 1323, and he is mentioned in the author index of Abu al-Barakat IBN KABAR, so that he probably lived before the first quarter of the fourteenth century. The additions to his name in the heading to his work indicate that he came from Cairo or spent most of his life there in some official post known as al-katib al- Misri (Egyptian secretarial official).
Yuhanna’s work, instigated by the Muslim teacher Abu ‘Ali ibn al-Hasan (or al-Husayn) ibn Mawhub, is a counterpart of numerous Islamic writings on theoretical and practical ethics. From the longing for immortality that mankind has, recognizing that this can be realized only in the next world, and assuming the desirability of a virtuous life in this world, the writer arrives at an apologia for Christianity. He gives fifteen arguments based on Christian moral doctrine.
Reasons for accepting the rules of Christian law are the existence of miracles and the moral benefit derived from the rules, which provide a greater benefit than philosophy does. Theoretical knowledge is requisite to practical activity, and so Yuhanna gave ways and means of achieving both. The whole work is a fundamental exposition of Christian moral doctrine made up of rational considerations and evangelical testimony.