Abraham bar Hiyya


Abraham bar Ḥiyya ha-Nasi, also known as Abraham Savasorda, Abraham Albargeloni, and Abraham Judaeus, was a Catalan Jewish mathematician, astronomer and philosopher who resided in Barcelona.
Bar Ḥiyya was active in translating the works of Islamic science into Latin, and was likely the earliest to introduce Arabic algebra into Christian Europe. He also wrote several original works on mathematics, astronomy, Jewish philosophy, chronology, and land surveying. His most influential work is his Ḥibbur ha-Meshiḥah ve-ha-Tishboret, translated in 1145 into Latin as Liber embadorum. A Hebrew treatise on practical geometry and Islamic algebra, the book contains the first known complete solution of the quadratic equation, and influenced the work of Leonardo Fibonacci.

Biography

Abraham bar Ḥiyya was the great-grandson of the Hezekiah Gaon. Bar Ḥiyya occupied a high position in the royal court, serving as minister of police, and bore the title of governor. Scholars assume that Bar Hiyya would have obtained this title in the court of Banu Hud of Saragossa-Lerida; there is even a record of a Jewish Savasorda there in the beginning of the 12th century. In his travelogues, Benjamin of Tudela mentions bar Ḥiyya living in Barcelona in the 1160s.
According to Adolph Drechsler, bar Ḥiyya was a pupil of Rabbi Moshe haDarshan and teacher of Abraham Ibn Ezra. He was held in high consideration by the ruler he served on account of his astronomical knowledge, and had disputes with learned priests, to whom he demonstrated the accuracy of the Jewish calendar. Abraham bar Hiyya is said to have been a great astronomer and wrote some works on astronomy and geography. One tells about the form of the earth, the elements and the structure of the spheres. Other works included papers on astrology, trigonometry, and music.
Some scholars think that the Magister Abraham who dictated De Astrolabio to Rudolf de Bruges was identical with Abraham bar Ḥiyya. Although the title "Sephardi" is always appended to his name, Barcelona was at the time no longer under Muslim rule, and therefore not part of Sepharad. Abraham Albargeloni thus belonged to the community of the Jews of Catalonia. Catalonia joined Provence in 1112 and Aragon in 1137, and thus the County of Barcelona became the capital of the Catalan-Aragonese Confederation called the Crown of Aragon. The kings of the Crown of Aragon extended their domains to the Occitan countries in what is now southern France. Abraham Albargeloni spent some time in Narbonne where he composed some works for the Jews of Provence, in which he complains of their Provençal Jewry's ignorance of mathematics.

Work

Abraham bar Ḥiyya was one of the most important figures in the scientific movement which made the Jews of Provence, the Jews of Catalonia, Spain, and Italy the intermediaries between Arabic science and the Christian world, in both his original works and his translations.
Bar Ḥiyya's Yesode ha-Tebunah u-Migdal ha-Emunah, probably intended to be a part of the preceding work. This is the celebrated geometry translated in 1145 by Plato of Tivoli, under the title Liber embadorum a Savasordo in hebraico compositus. Fibonacci made the Latin translation of the Ḥibbūr the basis of his Practica Geometriae, following it even to the sameness of some of the examples.
Bar Ḥiyya also wrote two religious works in the field of Judaism and the Tanach: Hegyon ha-Nefesh on repentance, and Megillat ha-Megalleh on the redemption of the Jewish people. The latter was partly translated into Latin in the 14th century under the title Liber de redemptione Israhel. Even these religious works contain scientific and philosophical speculation. His Megillat ha-Megalleh was also astrological in nature, and drew a horoscope of favourable and unfavourable days. Bar Ḥiyya forecasted that the Messiah would appear in AM 5118.
Abraham bar Ḥiyya wrote all his works in Hebrew, not in Judaeo-Arabic of the earlier Jewish scientific literature, which made him a pioneer in the use of the Hebrew language for scientific purposes.

Other notable works

Abraham bar Ḥiyya co-operated with a number of scholars in the translation of scientific works from Arabic into Latin, most notably Plato of Tivoli with their translation of Ptolemy's Tetrabiblos in 1138 at Barcelona.. There remains doubt as to the particulars: a number of Jewish translators named Abraham existed during the 12th century, and it is not always possible to identify the one in question. Known translations of bar Ḥiyya include:
In the preface to Ẓurat ha-Areẓ, bar Ḥiyya modestly states that, because none of the scientific works such as those which exist in Arabic were accessible to his brethren in France, he felt called upon to compose books which, though containing no research of his own, would help to popularize knowledge among Hebrew readers. His Hebrew terminology, therefore, occasionally lacks the clearness and precision of later writers and translators.

Philosophy

Bar Ḥiyya was a pioneer in the field of philosophy: as shown by Guttmann in refutation of David Kaufmann's assumption that the Hegyon ha-Nefesh was originally written in Arabic, Abraham bar Ḥiyya had to wrestle with the difficulties of a language not yet adapted to philosophic terminology.
Whether composed especially for the Ten Days of Repentance, as Rapoport and Rosin think, or not, the object of the work was a practical, rather than a theoretical, one. It was to be a homily in four chapters on repentance based on the Hafṭarot of the Day of Atonement and Shabbat Shuvah. In it, he exhorts the reader to lead a life of purity and devotion. At the same time he does not hesitate to borrow ideas from non-Jewish philosophers, and he pays homage to the ancient Greek philosophers who, without knowledge of the Torah, arrived at certain fundamental truths regarding the beginning of things, though in an imperfect way, because both the end and the divine source of wisdom remained hidden to them. In his opinion the non-Jew may attain to as high a degree of godliness as the Jew.

Matter and Form

Abraham bar Ḥiyya's philosophical system is neoplatonic like that of ibn Gabirol and of the author of Torot ha-Nefesh, as Plotinus stated:
Says Abraham bar Ḥiyya, in common with Aristotle, and others:
For after all, says he with Plato, the soul in this world of flesh is, as it were, imprisoned, while the animal soul craves for worldly pleasures, and experiences pain in foregoing them. Still, only the sensual man requires corrections of the flesh to liberate the soul from its bondage; the truly pious need not, or rather should not, undergo fasting or other forms of asceticism except such as the law has prescribed. But, precisely as man has been set apart among his fellow creatures as God's servant, so Israel is separate from the nations, the same three terms being used by the prophet for Israel's creation as for that of man in Genesis.

Three Classes of Pious Men

Like Baḥya, Abraham bar Ḥiyya distinguishes three classes of pious men:
  1. such as lead a life altogether apart from worldly pursuits and devoted only to God.
  2. such as take part in the world's affairs, but are, as regards their conduct, ruled only by the divine laws and statutes without concerning themselves with the rest of men
  3. such as lead righteous lives, but take care also that the wrong done outside of their sphere is punished and the good of all the people promoted.
In accordance with these three classes of servants of God, he finds the laws of the Torah to be divided into three groups:
  1. The Decalogue, containing the fundamental laws with especial reference to the God-devoted man who, like Moses, lives solely in the service of God. The first of the Ten Commandments, which he considers merely as an introductory word, accentuates the divine origin and the eternal goal of the Law; the other nine present the various laws in relation to God, to domestic life, and to society at large. Each of these three classes again refers either to the heart or sentiment, to the speech or to the action of man.
  2. The group of laws contained in the second, third, and fourth books of Moses, intended for the people of Israel during their wandering in the desert or during the Exile, to render them a holy congregation relying solely upon the special protection of God without resorting to warfare.
  3. The Deuteronomic legislation intended for the people living in an agricultural state and forming a "kingdom of justice." However, in the time of the Messianic redemption, when the evil spirit shall have vanished altogether, when the sensual man shall have become a spiritual one, and the passions that created hatred and strife shall have given way to love of man and to faithful obedience to the will of God, no other laws than those given to the God-devoted one in the Decalogue—the law written upon the heart of man—will be necessary. Men, imbued solely with love for their fellows, free from sin, will rise to the standard of the God-devoted man, and, like him, share in the eternal bliss of God.
Guttmann has shown that Naḥmanides read and used the Hegyon ha-Nefesh, though occasionally differing from it; but while Saadia Gaon is elsewhere quoted by Abraham bar Ḥiyya, he never refers to him in Hegyon. Characteristic of the age is the fact that while Abraham bar Ḥiyya contended against every superstition, against the teḳufah, against prayers for the dead, and similar practises, he was, nevertheless, like Ibn Ezra, a firm believer in astrology. In his Megillat ha-Megalleh he calculated from Scripture the exact time for the advent of the Messiah to be the year of the world 5118. He wrote also a work on redemption, from which Isaac Abravanel appropriated many ideas. It is in defense of Judaism against Christian arguments, and also discusses Mohammed, "the Insane"; announcing the downfall of Islam, according to astrological calculation, for the year 4946 A.M.

Mathematics

Bar Ḥiyya's Ḥibbur ha-meshīḥah ve-ha-tishboret contains the first appearance of quadratic equations in the West.
Bar Ḥiyya proved by geometro-mechanical method of indivisibles the following equation for any circle:, where is the surface area, is the circumference length and is radius. The same proof as appears in the commentary of the Tosafists on the Babylonian Talmud.

Footnotes