Moses ben Maimon was born in Cordova, Spain in 1135, into an old
Rabbinical family. Because of religious persecution, the family
moved several times, finally settling in Egypt, where Maimonides
became head of the Jewish community and physician to the Sultan.
His major works were a commentary on the Mishnah; a law code (the
Mishneh Torah) that covered all 613 commandments; and a
philosophical work (the Guide for the Perplexed) on Jewish beliefs
and their reconciliation with Greek philosophy. He also wrote many
other works on the Talmud and on other topics such as medicine, as
well as many letters and responsa. He died in Egypt in 1204.
The Mishneh Torah alone would make Maimonides one of the most important people in the history of Judaism; it was the only law code that covered the entire halachah. If we add to this his many other major works (the commentary on the Mishnah; the Guide for the Perplexed) and his expertise in other fields (especially in medicine), he stands out as probably the greatest Jew of the past millenium.
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