Based on what the author said, we can infer that they would most likely believe that Islam C- was able to expand because of beliefs shared with other pre-existing religions.
Herbert J. Muller believed that:
This shows that Islam was related to other religions at the time that practiced similar beliefs such as Christianity and Judaism in that they were both monotheistic. The difference however, was that Islam was purer.
In conclusion, the author believed that Islam spread because it shared beliefs with other religions.
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