A heresy is often defined as an aberration or rejection of doctrine of an established belief or custom. To better determine the origin of Islam and whether it began as a heresy of Christianity, it would be helpful to look back to the first Christian theologian who dealt with the rise of Islam, John of Damascus. In the early 8th century John wrote the Heresy of the Ishmaelites, which is the earliest apologetic treatise against Islam. John never referred to the “coercive” religion of the Ishmaelites as “Islam,” but he strongly indicated that it was false, and that it was indeed a heresy. He also said that “Mahmed” was a false prophet inspired by an Arian monk. In addition, John recognized that the beliefs of the Ishmaelites were a direct antithesis to the main beliefs of historic Christianity since they rejected that Jesus Christ was the actual Son of God, that God is a Trinity, and that Jesus Christ died on a cross and rose from the dead.
This paper will summarize the insight from John of Damascus and then compare his assessment with new evidence from archaeology, numismatics, and contemporary non-Muslim written accounts that tell a very different story from the traditional Muslim account promoted by Muslims today. The most recent evidence indicates that Islam may have developed from a Nabataean heresy of Christianity, similar to Arianism, that was centered in Petra rather than Mecca. This “Arab” Christianity may be understood as “proto-Islam,” and from Abd al-Malik’s time (685 AD) it may have been an Arab version of Christianity that praised Jesus as the chosen prophet, even the “Mahmed,” (“chosen one,” “praised one,”) but rejected him as the Son of God. Thus, from the time of John of Damascus to the present, mounting evidence continues to strengthen John’s assertion that Islam is indeed a heresy of Christianity.