Johnson relates in his book how before Muhammad’s time, there were some twenty Jewish tribes in his immediate vicinity. It is obvious that he was hugely influenced by Judaism. What a strange world it would be if he had conquered the entire Middle East not for Islam, but for Judaism. What if the Arabs were Jews and not Muslims? These extraordinary chances of History convince me more and more that all religions have intrinsic worth and are valuable in different ways to different peoples.

What Paul Johnson says is this:

What Mohammad seems to have wanted to do was to destroy the polytheistic paganism of the oases culture by giving to the Arabs a Jewish ethical monotheism in a language they could understand and in turn adapted to their ways. He accepted the Jewish God and their prophets; the idea of fixed law embedded in scripture the Koran being an Arabic substitute for the Bible an addition of an oral law applied in religious courts.

Mohammed’s development of a separate religion began when he realized that the Jews of Medina were not prepared to accept his arbitrary, contrived Arab revision of Judaism.

Had Mohammad possessed the skill and patience to work out the Arab Halakhas, the result might have been different.