From: Thomas Hockey et al. (eds.). The Biographical Encyclopedia of Astronomers, Springer Reference. New York: Springer, 2007, pp. 553-555

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Ibn ʿEzra: Abraham ibn ʿEzra

Tamar M. Rudavsky

BornTudela, (Navarra, Spain), circa 1089

DiedRome, (Italy), or possibly Palestine, circa 1167

Abraham ibn ʿEzra was a poet, grammarian, biblical exegete, philosopher, astronomer, astrologer, and physician. He lived in Spain until 1140 and then left Spain for a period of extensive wandering in Lucca, Mantua, Verona, Provence, London, Narbonne, and finally Rome. It was during the latter period that most of his works were composed. His wanderings forced him to write in Hebrew as well as in Latin, a fact that perhaps saved his works from oblivion. Like his teacher Abū al‐Barakāt, his son Isaac converted to Islam.

Ibn ʿEzra is best known for his biblical commentaries, which are written in an elegant Hebrew, replete with puns and word plans. These commentaries were commenced in Rome when he was already 64. Ibn ʿEzra was the first Jewish author to interpret a significant number of biblical events in an astrological way and to explain certain commandments as defenses against the pernicious influence of the stars.

Because of his constantly alluding to “secrets” in these commentaries based on astrological doctrines, Ibn ʿEzra's works inspired numerous supercommentaries. Ibn ʿEzra himself claimed that only the individual schooled in astrology, astronomy, or mathematics would understand these commentaries properly. Perhaps the most famous commentator upon Ibn ʿEzra was Spinoza, who adduced “Aben Ezra, a man of enlightened intelligence and no small learning,” in support of his own contention that Moses could not have written the Pentateuch. Although Ibn ʿEzra did not write any specifically philosophical works, he was strongly influenced by the Jewish Neoplatonist philosopher Solomon ibn Gabirol, and his works contain much Neoplatonic material.

Although Ibn ʿEzra was one of the foremost transmitters of Arabic scientific knowledge to the West, most of his scientific works are extant in manuscript only. Interestingly, most of his works appear in two or more versions; most scholars agree that in as much as Ibn ʿEzra was an itinerant scholar wandering from city to city, he would write new versions for each group of patrons he encountered.

The first group of treatises is devoted to teaching skills related primarily to astronomy and mathematics, as well as the use of scientific tools and instruments. The major works in this group are Sefer ha‐mispar (The book of the number), designed to be a basic textbook in mathematics; Sefer taʿamei ha‐luhot (The book of the reasons behind the astronomical tables), a treatise written in four different versions (two in Hebrew and two in Latin) to provide astronomical and astrological knowledge to persons interested in using astronomical tables; Keli ha‐nehoshet (The instrument of brass, i. e., the astrolabe), a technical manual, written in three different Hebrew versions as well as a Latin version, designed to teach the astronomical and astrological uses of the astrolabe; Sefer ha‐ʿibbur (The book of intercalation), written in two versions, designed to establish the Jewish calendar and explain its fundamentals; and, finally, Sefer ha‐ʾehad (The book on the unit), a short mathematical treatise devoted to the attributes of the numbers.

The second group of treatises comprises astrological works exclusively and includes both astrological textbooks and a series of astrological works that deal with the various branches of astrology. In addition to these treatises, Ibn ʿEzra translated into Hebrew a no longer extant Arabic scientific treatise, Ibn al‐Muthannā's Commentary on the Astronomical Tables of al‐Khwārizmī. This work includes Ibn ʿEzra's introductory assessment of the transmission of Hindu and Greek astronomy to the Arabic sciences.

Because Ibn ʿEzra was one of the first Hebrew scholars to write on scientific subjects in Hebrew, he had to invent many Hebrew terms to represent the technical terminology of Arabic. For example, he introduced terms for the center of a circle, for the sine, and for the diagonal of a rectangle. He describes his own research as hakmei ha‐mazzalot (science of the zodiacal signs), a term he uses often to refer to a number of branches of science: astrology, mathematics, astronomy, and the regulation of the calendar. In as much as the purpose of these works was primarily to educate and introduce scientific findings to a lay audience, they serve as an excellent source of learning about scientific texts available in 12th‐century Spain.

As noted by Shlomo Sela, one of Ibn ʿEzra's main aims was to “convey the basic features of Ptolemaic science, astronomical as well as astrological, as it was transformed by the Arabic sciences, especially in al‐Andalus” (Sela, 2000, p. 168). Thus, for example, his best‐known work, Beginning of Wisdom, functions as an introductory astrological textbook and deals with the zodiacal constellations and planets, their astrological characteristics, and more technical aspects of astrology. Ibn ʿEzra's star list appears as a section of his work The Astrolabe. The list is given in the form of a paragraph, in which the coordinates are given in Hebrew alphabetic numerals, and the Arabic names are transliterated into Hebrew characters. As Bernard Goldstein has pointed out, many of the discrepancies between Ibn ʿEzra's star positions and those in the Greek text of the Almagest can be traced to the Arabic versions of the Almagest. In his translation of Ibn al‐Muthannā's Commentary, Ibn ʿEzra describes the early stages of astronomy among the Arabs, listing a number of prominent astronomers whose works he consulted. The Hebrew versions of Ibn al‐Muthannā's commentary have been useful for interpreting a set of canons for tables with Toledo as the meridian preserved in a Latin manuscript.

According to John North, Abraham ibn ʿEzra was the earliest scholar to record one of the seven methods for the setting up of the astrological houses. This method was used, for example, by Gersonides who made use of Ibn ʿEzra's Book of the World in his prognostication of 1345.

In as much as Abraham Ibn ʿEzra's works were widely copied in Hebrew and translated into European languages, he was responsible for the availability of much Arabic science in Hebrew and Latin, and he helped to spread the new Hebrew astronomical literature throughout Europe.

Selected References

Friedlander, M. (1877). Essays on the Writings of ibn Ezra. London. (Reprint, Jerusalem, 1944.)

Goldstein, Bernard R. (1967). Ibn al‐Muthannā's Commentary on the Astronomical Tables of al‐Khwārizmī. Two Hebrew versions, edited and translated, with an astronomical commentary by Bernard R. Goldstein. New Haven: Yale University Press.

——— (1985). “Star Lists in Hebrew.” Centaurus 28: 185–208.

——— (1996). “Astronomy and Astrology in the Works of Abraham ibn Ezra.” Arabic Sciences and Philosophy 6: 9–21.

Halbronn, Jacques (1966). “Le diptyque astrologique d'Abraham Ibn Ezra et les cycles planétaires du Liber Rationum.” Revue des études juives 155: 171–184.

Ibn ʿEzra, Abraham (1845). Keli haNehoshet, edited by H. Edelman. Königsberg.

——— (1874). Sefer haʿIbbur, edited by S. Z. H. Halberstam. Lyck.

——— (1895). Sefer haMispar, Das Buch der Zahl, edited by Moritz Silberberg. Frankfurt am Main.

——— (1939). Sefer haMivharim, edited by Judah Loeb Fleischer. Jerusalem.

——— (1951). Sefer ha‐Teʾamim, edited by Judah Loeb Fleischer. Jerusalem.

——— (1971). “Sefer haʿOlam.” In Sefer Mishpetei haKokhavim, edited by Meʾir Yshaz Bakʾal, pp. 36–54. Jerusalem.

——— (1985). “Sefer Yesod Mora ve‐Yesod Torah.” In Yalqut Abraham ibn Ezra. New York.

——— (1988). Ibn Ezra's Commentary on the Pentateuch. (Translated by H. Norman Strickman and Arthur M. Silver. New York: Menorah Pub. Co.)

Langermann, Y. Tzvi (1993). “Some Astrological Themes in the Thought of Abraham ibn Ezra.” In Rabbi Abraham ibn Ezra: Studies in the Writings of a Twelfth‐Century Jewish Polymath, edited by Isadore Twersky and Jay M. Harris, pp. 28–85. Cambridge Massachusetts: Harvard University Press.

——— (2000). “Hebrew Astronomy: Deep Soundings from a Rich Tradition.” In Astronomy Across Cultures, edited by Helaine Selin, pp. 555–584. Dordrecht: Kluwer.

Levy, Raphael (ed. and trans.) (1927). The Astrological Works of Abraham ibn Ezra: A Literary and Linguistic Study with Special Reference to the Old French Translation of Hagin. Baltimore: Johns Hopkins University Press.

Levy, Raphael and F. Cantera (eds. and trans.) (1939). The Beginning of Wisdom, An Astrological Treatise by Abraham ibn Ezra. Baltimore: Johns Hopkins University Press.

Millás Vallicrosa, José María (1947). El libro de los fundamentos de las Tables astronómicas de R. Abraham ibn Ezra. Madrid: Consejo Superior de Investigaciones Científicas.

North, John D. (1986). Horoscopes and History. London: Warburg Institute.

Sela, Shlomo (1997). “Scientific Data in the Exegetical‐Theological Work of Abraham Ibn Ezra: Historical Time and Geographical Space Conception” (in Hebrew). Ph.D. diss., Tel Aviv University.

——— (1999). Astrology and Biblical Exegesis in the Thought of Abraham Ibn Ezra (in Hebrew). Ramat‐Gan.

——— (2000). “Encyclopedic Aspects of Abraham Ibn Ezra's Scientific Corpus.” In The Medieval Hebrew Encyclopedia of Science and Philosophy, edited by S. Harvey, pp. 154–170. Dordrecht: Kluwer.

——— (2001). “Abraham ibn Ezra's Scientific Corpus–Basic Constituents and General Characterization.” Arabic Sciences and Philosophy 11: 91–149. (Sela has managed to ascertain the existence of 26 different treatises, representing 14 distinct treatises in all, written mostly in Hebrew and partly in Latin.)