What is the theme in Muhammad: A Biography of the Prophet by Karen Armstrong?

Filling a need is another theme in the book. Muhammad's teachings and the formation of Islam fulfilled a need in seventh-century Arab society. The pagan society was based on the tribal law and traditions. Loyalty was to the chief and tribe, not to any Arab identity. The chief was the protector for the members of the clan. The society accepted the fact that any tribe's action against another tribe brought about an equal amount of retribution. As a result, there was a lot of bloodshed and fighting and many people were tired of the situation. Muhammad offered the Arabs an alternative to this kind of life which is why so many people were receptive to conversion.