The life of Jesus: No angel Zealot: The Life and Times of Jesus of Nazareth. By Reza Aslan. Random House; 296 pages; $27. IN HIS earlier book about Islam, Reza Aslan, an Iranian-born American writer, presented a subtle view of the different layers of truth that can be found in sacred writings. For example, he explained that stories about Muhammad's childhood are not meant to relate to historical events, but rather "to elucidate the mystery of the prophetic experience." In any case, he added teasingly, myth is always true somehow; if it did not express a powerful truth, it would not last. The sensibility that Mr Aslan brings to his latest book, about the founder of another monotheism, is by comparison rather one-dimensional, although his considerable gifts as a storyteller and populariser of complex religious ideas remain intact. The purpose of "Zealot" is not to contemplate Jesus of Nazareth as a source of ultimate meaning, but to investigate and describe the story of his life. The book's underlying assumption is that if Jesus has any significance at all, it is to be found in the facts of his earthly existence. And these facts, Mr Aslan maintains, are often diametrically opposed to the story set out in the New Testament - which is one the author himself once embraced as a 15-year-old convert to evangelical Christianity. The trouble is that neither narrative - the familiar one or his alternative - can be established as incontrovertible, so Mr Aslan's tendency to make pronouncements with blithe certainty can grate. Only periodically does he throw in an appropriate expression of doubt. Far from being a pacifist, Jesus for Mr Aslan was the leader of a nationalist revolt against Rome who was punished for sedition, not blasphemy. In other words, Jesus meant it when he said "I have not come to bring peace, but the sword," whereas sayings like "My kingdom is not of this world" may well have been made up. As for the commandment to "Render unto Caesar what is Caesar's and unto God what is God's," that is a statement of theocratic resistance to Roman rule. It is amazing, in Mr Aslan's condescending view, that so many people have failed to see this. He argues that the universalist pacifism ascribed to Jesus was superimposed on him several decades after his death, in the climate created by the destruction of the Jerusalem Temple in 70AD. Once Jewish resistance to Rome was more or less quashed, followers of Jesus consciously or unconsciously refashioned their faith into one that meekly accepted imperial authority and could spread easily through a multinational empire. Many religious scholars believe that texts should be studied and decoded in the context of the eras in which they were written. But Mr Aslan places enormous, and perhaps excessive, emphasis on the explanatory power of context. Because history reveals at least something of the role of itinerant preachers who challenged Roman rule in the quarrelsome Jewish world, he assumes it is possible to locate Jesus in that world. Context is necessary for anyone trying to pin down the historical Jesus, but such arguments can go too far. At their most ambitious, they purport to decode with perfect accuracy any piece of religious text, laying bare both the facts that lie behind it and the reasons why those facts were refracted in a certain way. That approach refuses to even acknowledge the possibility of prophecy, which means the ability of individuals to discern important truths about the world in ways that rise above the circumstances of their lives. How people respond to prophets and their claims is an existential choice, but a belief that prophets exist - that not all concepts can be reduced to historical context - is central to any religious faith. This means that appreciating the possibility of prophecy (whatever one chooses to make of it) is vital to the work of a religious historian. Mr Aslan has shown elsewhere that he understands this, but there is not much sign of this insight in his latest book.