Why is it that Muhammad’s relations with Medina’s Jews and Christians seem not to have worked out?

It’s hard to reconstruct the story with confidence, but one thing seems clear: it wasn’t a simple case of Muhammad demanding conversion to Islam and being rebuffed. For a time, at least, his goal seems to have been to unite the Abrahamic religions but not to merge them. In an apparently authentic document known as the Constitution of Medina, Muhammad is deemed the arbiter of disputes in Medina—hence, in effect, its leader—but the separateness of the Jewish religion is acknowledged. Similarly, the revelation that justified that initial attack on the Meccan caravan cast it as an act of preemptive defense on behalf of the distinct Abrahamic faiths. “For if God had not enabled people to defend themselves against one another, monasteries and churches and synagogues and mosques—in which God’s name is abundantly extolled—would surely have been destroyed.”

For purposes of municipal government, it was best that all Medinans see Muhammad not just as a defender of their right to worship, but as a man with genuine divine authority. So he wanted to show Christians and Jews that they could grant the validity of his pronouncements without abandoning their own traditions. He explained that God had “sent down the Torah and the Gospel aforetime, as guidance to the people,” and now had sent down the Koran “confirming what was before it.” And he encouraged Jews and Christians to focus on the Abrahamic common denominator: “O followers of earlier revelation! Come unto that tenet which we and you hold in common: that we shall worship none but God, and that we shall not ascribe divinity to aught beside Him.”

Of course, the larger the zone of agreement among the Abrahamic faiths, the more completely Christians and Jews could acknowledge Muhammad’s authority. The more common rituals the faiths could share, and the more theological differences they could iron out, the more cohesive a polity Medina could be.

Here Muhammad was willing to bear some of the burden of adaptation. Once in Medina, he decided that his followers should have an annual twenty-four-hour fast, just as Jews did on Yom Kippur. He even called it Yom Kippur—at least, he used the term some Arabian Jews were then using for Yom Kippur. And the Jewish ban on eating pork was mirrored in a Muslim ban on eating pork, probably first enunciated in Medina. Muhammad also declared that his followers should pray facing Jerusalem. Indeed, so thoroughly did Muhammad intermingle Islamic and Jewish ritual that half a century after his death, a Byzantine Christian would describe Muhammad as a “guide” who had instructed Arabs in the Torah.

But reaching out to Christians was more complicated. Muhammad had staked out the basic Muslim position on Jesus back in Mecca. He had lauded Jesus as a great prophet but had refused to say he was the son of God. Yes, he said, Jesus was sent as a sign from God; and yes, he was of virgin birth. But “It beseemeth not God to beget a son.”

This position may have had an essentially logical basis. Among the Arab polytheists Muhammad denounced in the course of his monotheistic mission were those who accepted the existence of Muhammad’s God, Allah, but insisted that Allah had daughters. No, Muhammad said, there was only one God—no daughter gods allowed (except during the overture to polytheists that, as we’ve seen, seems to have created the subsequently erased “satanic verses”). Well, if God couldn’t have daughters, how could he have a son? One Meccan sura suggests that this is a rejoinder Muhammad himself had received from pagan skeptics in a rare moment when he was treating Jesus with the sort of reverence reserved for divinity. “They said, ‘Are our gods or is he the better?’ They put this forth … only in the spirit of dispute. Yea, they are a contentious people.”

This may have been a theological turning point for Muhammad: he went as far as he could toward embracing Jesus’s divinity and then realized he was painting himself into a corner, undermining the monotheistic thrust of his message.

That raises a question: Why would Muhammad bother praising Jesus at all if he was going to deny his divinity and thus alienate all true Christians?

Here the phrase “true Christians” misleads. As we’ve seen, ancient Christianity was a motlier thing than the seamless version of it that was later read back into history. Remember the Ebionites, the “Jewish” Christians who considered Jesus the adopted son of God—a messiah but a human one? We don’t know what happened to them after their existence was noted in fourth-century texts, but their influence certainly could have drifted toward Arabia. J. M. Rodwell, a nineteenth-century British translator of the Koran, deemed it “quite clear that Muhammad borrowed … from the doctrines of the Ebionites.” If Ebionite doctrines were indeed floating around Arabia, some Ebionites—or people rather like them—probably were, too. And Muhammad could have hoped to win them over by revering a merely human Jesus.

And the Ebionites weren’t the only source of Christian diversity. Because Arabia had commercial contact not just with Byzantine Syria to the north but with the Persian Empire to the east, there were “Nestorian” Christians, who believed Christ, though divine, had a more human side than Roman or Greek Christians allowed. Persia also featured Manichaeans, who considered Jesus a prophet but not divine. And then there were the more orthodox Christians, from Syria. All told, it was a smorgasbord of “Christian” belief.

For that matter, Arabian Jews in Muhammad’s day may have been anywhere along the spectrum from evangelically apocalyptic to sedately conservative. Mecca in the seventh century was kind of like the world today, a place where diverse cultures were coming together, and the time was ripe for creative synthesis. The tendency to analyze the Koran by dividing Muhammad’s audience into “Christians,” “Jews,” and “pagans” understates both the cultural complexity of the time and the subtlety of the political challenge Muhammad faced.

All of this could explain the otherwise mysterious fact that in Medina, Muhammad continues to seek the allegiance of Christians while denouncing “Christian” theology more clearly than in Mecca. Here, for the first time, he rejects the doctrine of the Trinity by name. “Say not, ‘Three,’” he advises followers of Jesus.

Yet even in this sura, while denying Jesus the status of God, Muhammad emphasizes how special he was, calling him Messiah and nodding toward the assertion in the Gospel of John that Jesus was an incarnation of the divine Logos, the “Word.” “People of the Book,” he says, “the Messiah, Jesus son of Mary, was only the Messenger of God, and His Word that He committed to Mary, and a Spirit from Him.” Muhammad also lauded Christian values; God, according to the Koran, gave Jesus the gospel and “put into the hearts of those who followed him kindness and compassion.”

Even if Muhammad could have sold Christians on this formula, he would still have faced a problem. He was calling Jesus the Messiah, and Jews were of the view that the Messiah hadn’t shown up yet. If Muhammad’s aspiration was indeed, as it sometimes seems, to build a common religious platform for Christians and Jews and then call that platform Islam, his work was cut out for him.