John succeeded his father as a key advisor to the Muslim ruler, Caliph Abd al-Malik (r. 685–705). After a long life of service in the public realm John left his public position in the early part of the eighth century in order to embrace a monastic lifestyle in a monastery near Jerusalem. John was a prolific writer, and among his writings there are two that address Islam: On Heresies 101, a lengthy section of a work that catalogs various heresies afflicting the church; and A Dialogue Between a Saracen and a Christian. Let us look briefly at the first of these works, On Heresies 101.

The early centuries of the church saw Christianity threatened by a number of theological heresies: Gnosticism, Arianism, and Pelagianism, to name but three. While history never repeats itself exactly, the essence of many of these heresies has reappeared from time to time in the long history of Christianity. For instance, postmodernity’s interest in spirituality, though it rages against Christianity, has numerous similarities to the lengthy battle against Gnosticism that occupied the church during the second and third centuries. Knowledge of the way that Christians in the past defended the faith against Gnosticism would provide helpful ways of responding to postmodern spirituality today.¹

Or what about the challenge, one of the greatest of today, posed by Islam’s attack on the Trinity and the deity of the Lord Jesus Christ?² Broadly speaking, evangelicals are woefully inadequate in their ability to respond to such an attack, for they rarely hear sermons on the Trinity and the incarnation. Here, the Fathers can help us enormously, for in replying to the Arians and then later to the Muslims they hammered out the biblical details of these two key doctrines. Consider the way that the theologian John of Damascus, also known as John Damascene or Yanah ibn Masur, a biblically informed Christian, responded to Islam during the early period of Muslim expansion.³ In a small book defending the faith and worldview of Islam, Rana Kabbani identifies John as “the progenitor of a long tradition of Christian ridicule of Muhammad and the Qur’ãn.”⁴ John does use some strong language about Islam, but it is clear that he has taken the time to understand Islamic views and thinking, and has even read the Qur’an in Arabic.⁵

John is often described as the last of the church fathers in the East, whose The Fount of Knowledge is the first great systematic theology to appear in the history of the church. He may very well have been an Arab by ethnicity, his family name being Masur, a name common among Syriac Christians of Arab descent.⁶ His grandfather, Masur ibn Sargun, played a key role in the surrender of Damascus to the Muslim army of Khalid ibn al-Walid (d.ca. 641). Early rulers of Syria were tolerant of the presence of Christians, and John’s grandfather became a key administrator in the Muslim government of the region. John’s father, Ibn Mansur, was known as an extremely devout Christian but also one of the most trusted officials in the Muslim regime. John succeeded his father as a key advisor to the Muslim ruler, Caliph Abd al-Malik (r. 685–705). After a long life of service in the public realm John left his public position in the early part of the eighth century in order to embrace a monastic lifestyle in a monastery near Jerusalem. John was a prolific writer, and among his writings there are two that address Islam: On Heresies 101, a lengthy section of a work that catalogs various heresies afflicting the church;⁷ and A Dialogue Between a Saracen and a Christian.⁸ Let us look briefly at the first of these works, On Heresies 101.

The text begins by defining Islam as the “still-prevailing superstition of the Ishmaelites that deceives people” and “the forerunner of the Antichrist.” By describing Islam as “still-prevailing” John indicates the political dominance of Islam in his area of the world. However, he critiques it as a deceptive error and identifies it with the Antichrist, an identification that has long prevailed among Christian authors.

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