MONTAGNE: So at what point and why did violent conversion become part of Islam's success? How does the sword fit into the teachings of Muhammad, or is that some sort of perversion of the teachings of Muhammad? Throughout the first, three, four years of his preaching, the vast majority of the message that Muhammad revealed to the Meccans had to do with financial reform and distributing the wealth to the poor and the needy. And people from all over the peninsula came to Mecca to worship their gods, but they also came in order to trade with one another, and the influx of money into this city had made the ruling aristocracy enormously wealthy. This was a sanctuary that housed all of the known gods in the Arabian Peninsula, including Jesus, including Abraham, including all of the various pagan gods as well. The reason that Mecca had become this financial empire was because of the Kaaba. ASLAN: Muhammad, when he felt that he was being called by God to become a prophet, to bring the God of the Jews and the Christians to the pagan Arab peoples, saw his first task not to be a religious reformation but to be a social reformation.

MONTAGNE: When Muhammad-it was revealed to him that he was a prophet, what were the key elements of his thinking that changed everything? And it quite clearly informed his own spiritual identity. This was just this religious melting pot that Muhammad grew up in and had access to. And most importantly, this was a city that was surrounded by a host of different religious groups, Jews and Christians and Zoroastrians from Iran, and a whole variety of various pagan groups. I mean, this was about the closest thing to an Arab cosmopolitan city that the ancient world had seen. REZA ASLAN (Author, 'No god But God'): Well, the Mecca that Muhammad was born into was, at that time, the financial, cultural, social and religious capital of the Arabian Peninsula. Aslan argues that Muhammad's seventh-century teachings were actually closer to those modern ideas. The real struggle is between Islam and Islam, a rivalry between a rigid, dogmatic brand of Islam and one that embraces modern notions of pluralism and tolerance. The West, he writes, is merely a bystander, a complicit casualty. In his book, 'No god But God,' Reza Aslan offers an intriguing premise. Reza Aslan is a scholar of Islam who takes a different view. That's the theory that the world is engaged in a battle between the forces of fundamentalist Islam and secular democracy. Since the September 11 attacks, we've heard a lot of warnings about a clash of civilizations.

No god but God by Reza Aslan