Rabbi Moshe ben Maimon, known by Jews as the Rambam and by the wider world as Maimonides (1138 to 1204), did something no one had done before him. He took the vast, tangled ocean of Talmudic law, a work assembled over roughly six hundred years by generations of sages in Babylonia and the Land of Israel, and he rewrote it as a single, clear, orderly code that any literate Jew could open and use.
His masterwork was called Mishneh Torah, the "Second Law," a bold title that implied his code was a companion to the Torah itself. The book was copied by scribes everywhere within years of its completion in 1180, and manuscripts of it spread from Cairo, where he lived as court physician to Saladin, across North Africa, Spain, Provence, Italy, Germany, and Yemen. No earlier rabbinic work had traveled so fast or been read so widely by so many.
But the Rambam did not stop at law. Against the atheism and skepticism of his century, he wrote many philosophical works arguing, among other things, that God created the universe from nothing, not from some pre-existing matter. And at the age of fifty, around 1190, he gave the world his most daring and difficult work, Moreh Nevukhim, the Guide of the Perplexed, a book written in Judeo-Arabic for Jewish intellectuals who felt torn between Torah and the philosophy of Aristotle.
Rabbi Judah Charizi (c. 1165 to 1225), poet and translator, produced a Hebrew version of the Guide and added an appendix to it, helping to carry Rambam's thought into communities that could not read the original Arabic. This passage from Harris's 1901 Hebraic Literature compresses a whole world-shaping career into a paragraph: the codifier of law, the defender of creation ex nihilo, and the guide for those who did not know whether to trust their reason or their tradition, taught by Maimonides to trust both.