Jesus the loving shepherd. Bringer of peace and justice. Teacher of universal morals. Jesus the rabbi. Jesus the philosopher. Jesus the apocalyptic prophet. Jesus the Christ of faith.

People have constructed many different Jesuses. For at least two centuries, scholars and popular writers have mined the Christian Gospels to “look behind” them, to create a portrait of Jesus, using purely modern methods: the historical Jesus as opposed to the Christ of faith. In his book “Zealot: The Life and Times of Jesus of Nazareth,” Reza Aslan follows this long tradition, settling on the hypothesis, also around for hundreds of years, that Jesus was a Jewish zealot, a rebel against Rome and the Romans’ local agents.

Mr. Aslan’s book has been greeted with unwarranted controversy. Some conservatives seem offended by merely the idea that a Muslim scholar would write a book about Jesus. This should be no more controversial than a Christian scholar’s writing a book about Islam or Muhammad. It happens all the time. Nor is Mr. Aslan’s thesis controversial, at least among scholars of early Christianity.

According to Mr. Aslan, Jesus was born in Nazareth and grew up a poor laborer. He was a disciple of John the Baptist until John’s arrest. Like John, Jesus preached the imminent arrival of the kingdom of God, which would be an earthly, political state ruled by God or his anointed, a messiah. Jesus never intended to found a church, much less a new religion. He was loyal to the law of Moses as he interpreted it. Jesus opposed not only the Roman overlords, Mr. Aslan writes, but also their representatives in Palestine: “the Temple priests, the wealthy Jewish aristocracy, the Herodian elite.”