Jewish science and philosophy in the Middle Ages were almost entirely domiciled in Islam. Isolated and scorned, and yet influenced by their neighbors, the Jews of medieval Christendom took refuge in mysticism, superstition, and Messianic dreams; no situation could have favored science less. Religion, however, encouraged the study of astronomy, for on this depended the correct determination of the holydays. In the sixth century the Jewish astronomers of Babylonia substituted astronomic calculation for direct observation of the heavens; they based the year on the apparent movements of the sun, and the months on the phases of the moon; gave Babylonian names to the months; made some months “full” with thirty days, some “defective” with twenty-nine; and then reconciled the lunar with the solar calendar by inserting a thirteenth month every third, sixth, eighth, eleventh, fourteenth, seventeenth, and nineteenth year in a nineteen-year cycle. In the East the Jews dated events by the Seleucid calendar, which began at 312 B.C.; in Europe, in the ninth century, they adopted the present “Jewish era,” anno mundi—“year of the world”—beginning with the supposed creation in 3761 B.C. The Jewish calendar is as clumsy and sacred as our own.

One of the earliest astronomers in Islam was the Jewish scholar Mashallah (d. c. 815). His De scientia motus orbis was translated from Arabic into Latin by Gerard of Cremona, and won wide acclaim in Christendom. His treatise De mercibus (On Prices) is the oldest extant scientific work in the Arabic tongue. The foremost mathematical treatise of the age22 was the Hibbur ha-meshihah— on algebra, geometry, and trigonometry—of Abraham ben Hiyya of Barcelona (1065-1136), who also composed a lost encyclopedia of mathematics, astronomy, optics, and music, and the earliest surviving Hebrew treatise on the calendar. Abraham ibn Ezra, in the next generation, found no conflict between writing poetry and advancing combinatorial analysis. These two Abrahams were the first Jews to write scientific works in Hebrew rather than in Arabic. Through such books, and a flood of translations from Arabic into Hebrew, Moslem science and philosophy invaded the Jewish communities of Europe, and broadened their intellectual life beyond purely rabbinical lore.

Profiting in some measure from Islamic science, but also recapturing their own traditions of the healing art, the Jews of this period wrote outstanding treatises on medicine, and became the most esteemed physicians in Christian Europe. Isaac Israeli (c. 855-c.955) acquired such fame as an ophthalmologist in Egypt that he was appointed physician to the Aghlabid court at Qairwan. His medical works, translated from Arabic into Hebrew and Latin, were acclaimed as classics throughout Europe; they were used as textbooks at Salerno and Paris, and were quoted, after 700 years of life, in Burton’s Anatomy of Melancholy (1621). Tradition describes Isaac as indifferent to wealth, an obstinate bachelor, and a centenarian. Probably contemporary with him was Asaf ha-Jehudi, the obscure author of a recently discovered manuscript reckoned to be the oldest extant medical work in Hebrew, and remarkable for its teaching that the blood circulates through the arteries and the veins; had he surmised the function of the heart he would have completely anticipated Harvey.23

In Egypt, after the arrival of Maimonides (1165), the medical art was dominated by Jewish practitioners and texts. Abu al-Fada of Cairo wrote the principal ophthalmological treatise of the twelfth century, and al-Kuhin al-Attar composed (c. 1275) a pharmacopoeia still used in the Moslem world. The Jewish physicians of southern Italy and Sicily served as one medium through which Arabic medicine entered Salerno. Shabbathai ben Abraham (913-70), called Donnolo, born near Otranto, was captured by Saracens, studied Arabic medicine at Palermo, and then returned to practice in Italy. Benvenutus Grassus, a Jerusalem Jew, studied at Salerno, taught there and at Montpellier, and wrote a Practica oculorum (c. 1250) which Islam and Christendom alike accepted as the definitive treatise on diseases of the eye; 224 years after its publication it was chosen as the first book to be printed on its theme.

Rabbinical schools, especially in southern France, gave courses in medicine, partly to provide rabbis with a secular income. Jewish physicians trained in the Hebrew academy at Montpellier helped to develop the famous Montpellier school of medicine. The appointment of a Jew as regent of the faculty in 1300 drew upon his people the wrath of the medical authorities in the University of Paris; the Montpellier school was forced to close its doors to Jews (1301), and the Hebrew physicians of the city shared in the banishment of the Jews from France in 1306. By this time, however, Christian medicine had been revolutionized by Jewish and Moslem example and influence. The Semitic practitioners had long since put behind them the theory of sickness as “possession” by demons; and the success of their rational diagnosis and therapy had weakened the belief of the people in the efficacy of relics and other supernatural means of cure.

The monks and secular clergy whose abbeys and churches housed relics and drew pilgrims found it hard to accept this revolution. The Church condemned the intimate reception of Jewish doctors into Christian homes; she suspected that these men had more physic than faith, and she dreaded their influence upon sick minds. In 1246 the Council of Béziėrs forbade Christians to employ Jewish physicians; in 1267 the Council of Vienna forbade Jewish physicians to treat Christians. Such prohibitions did not prevent some prominent Christians from availing themselves of Jewish medical skill; Pope Boniface VIII, suffering from an eye ailment, called in Isaac ben Mordecai;24 Raymond Lully complained that every monastery had a Jewish physician; a papal legate was shocked to find that this was also the fate of many nunneries; and Christian kings of Spain enjoyed Jewish medical care down to the reign of Ferdinand and Isabella. Sheshet Benveniste of Barcelona, physician to King James I of Aragon (1213-76), wrote the chief gynecological treatise of his time. The Jews lost their ascendancy in the medical practice of Christendom only when Christian universities, in the thirteenth century, adopted rational medicine.

For so mobile and scattered a people the Jews contributed little to the science of geography. Nevertheless the outstanding travelers of the twelfth century were two Jews—Petachya of Ratisbon and Benjamin of Tudela—who wrote valuable Hebrew narratives of their journeys through Europe and the Near East. Benjamin left Saragossa in 1160, leisurely visited Barcelona, Marseilles, Genoa, Pisa, Rome, Salerno, Brindisi, Otranto, Corfu, Constantinople, the Aegean Isles, An-tioch, every important city in Palestine, and Baalbek, Damascus, Baghdad, and Persia. He returned by ship through the Indian Ocean and the Red Sea to Egypt, Sicily, and Italy, and thence overland to Spain; he reached home in 1173, and died soon afterward. His main interest was in the Jewish communities; but he described with fair accuracy and objectivity the geographic and ethnic features of each country on his route. His account is less fascinating, but probably more reliable, than the reports made by Marco Polo a century later. It was translated into nearly all European languages, and remained till our time a favorite book with the Jews.25

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