The history of the Christians saw two waves of division. The first was doctrinal and early, turning on disagreement over the nature of the Messiah, peace be upon him, and from it the ancient Eastern churches separated in the fifth century. The second came later: the Eastern Church parted from the Western in 1054, and Protestantism broke from Catholicism in 1517 — over the authority of the pope and the source of law, not over the nature of the Messiah, for the three communions agree on the rulings of the early councils.

The Qurʾān pointed to this division and to the alteration that entered the earlier scriptures, and made clear that the final message came as a guardian over what preceded it, confirming and correcting it.

The Causes of the Division

Doctrine was settled at the Church councils rather than by a text transmitted beyond doubt: Nicaea in 325 CE decided the divinity of the Messiah, peace be upon him; Constantinople in 381 decided the divinity of the Holy Spirit; and Chalcedon in 451 decided the two natures — and from it the ancient Eastern churches split away.

To this is added the absence of an unbroken chain of transmission: the Christians hold no text written down in the language the Messiah spoke — Aramaic; the Gospels were written in Greek decades after him, and were attributed to their authors in the second century rather than when they were written. The door of interpretation was thrown wide open.

The Gospels themselves then differ in reporting events; among the clearest instances is the difference in the genealogy of the Messiah between Matthew (1:1–16) and Luke (3:23–38), in the number of generations and the names of the forefathers.

How Islam Lifted the Dispute

Islam lifted this dispute by restoring pure monotheism and declaring God free of any partner or child — Sūrat al-Muʾminūn, verse 91.

The Qurʾān set out the reality of Jesus son of Mary, peace be upon him: that he is the servant of God and His messenger, no more and no less — Sūrat al-Māʾidah, verse 75.

And God made the Qurʾān a criterion over what came before it, preserved from addition and loss, so that it became the reference to which those disputes are returned, its text not itself in contention.

Closing

Historical and textual scrutiny together indicate that the division of the Christians was no passing accident, but the fruit of a broken chain of transmission and of alteration entering the text. And that the final message came with what lifts this disagreement at its root: pure monotheism; a prophet known for what he is, neither raised above his station nor denied his due; and a preserved book to return to.