Born: 1092 in Tudela, Emirate of Saragossa (now Spain)
Died: 1167 in Calahorra, Spain

Rabbi Ben Ezra lived in Muslim Spain. Little is known of his life except that he was on friendly terms with the eminent poet and philosopher Judah ha-Levi, who some historians believe was ibn Ezra's father-in-law. Ibn Ezra made his reputation as a scholar and a poet. It is recorded that during this period of his life, up to 1140, he travelled to North Africa and possibly visited Egypt.

From 1140 to 1160 ibn Ezra's life changed markedly. He was forced to wander throughout Europe during this period and he eventually settled down in Rome, then Lucca, for a few years before his death. It was during this latter period of his life that he composed his most famous works. In addition to his poetry, ibn Ezra wrote on [7]:-

... grammar, exegesis, philosophy, medicine, astronomy, and astrology.

In addition to these topics, ibn Ezra wrote on permutations and combinations, the calendar, the astrolabe, and Biblical studies. He is of particular importance because he spread the learning of the Arabs through Europe at a time when scholarship in Christian Europe had been been neglected for five hundred or more years.

Of the most interest to us in this archive devoted to the history of mathematics is ibn Ezra's work on numbers. He wrote three treatises on numbers which helped to bring the Indian symbols and ideas of decimal fractions to the attention of some of the learned people in Europe. The Book of the Unit is a work on the Indian symbols 1, 2, 3, 4, 5, 6, 7, 8, 9. A second work is the Book of the Number which describes the decimal system for integers with place values from left to right. In this work ibn Ezra uses zero which he calls galgal (meaning wheel or circle). Despite ibn Ezra's books, these ideas would not become accepted into mainstream European mathematics for several more centuries.

Ibn Ezra translated al-Biruni's commentary on al-Khwarizmi's tables and made interesting comments on the introduction of Indian mathematics into Arabic science in the 8^th century. Historians of science try today to quantify precisely how much Arabic mathematics was influenced by knowledge of Indian mathematics, so ibn Ezra's writing on this topic are carefully studied.

Ibn Ezra's writings on grammar and poetry were often motivated by the "paytanim" [2]:-

Synagogues began ... to appoint official precentors, part of whose duty it was to compose poetical additions to the liturgy on special Sabbaths and festivals. The authors were called "paytanim" (from the Greek poietes, "poet"), their poems "piyyutim". The keynote was messianic fervour and religious exuberance. Besides employing the entire biblical, Mishnaic, and Aramaic vocabularies, the paytanim coined thousands of new words. ... Abraham ibn Ezra... attacked the language and style of the early paytanim; he [was] the first to use Arabic metres in religious poems.

In fact to ibn Ezra there was no conflict between science and religion for he considered that science and astrology were at the basis of Jewish learning [7]:-

1. M Levey, Biography in Dictionary of Scientific Biography (New York 1970-1990). 
   http://www.encyclopedia.com/topic/Abraham_ben_Meir_Ibn_Ezra.aspx
2. Biography in Encyclopaedia Britannica. 
   http://www.britannica.com/eb/article-9041914/Abraham-ben-Meir-ibn-Ezra

Books:

1. F D Esteban (ed.), Abraham ibn Ezra and his age : Proceedings of the international symposium (Madrid, 1990).
2. G B Sarfatti, Mathematical terminology in Hebrew scientific literature of the Middle Ages (Jerusalem 1968).
3. I Twersky and J Harris (eds.), Rabbi Abraham ibn Ezra : Studies in the writings of a twelfth century Jewish polymath (Cambridge MA, 1993).

Articles:

1. A R Amir-Moéz, Comparison of the methods of Ibn Ezra and Karkhi, Scripta Math. 23 (1957), 173-178.
2. E Craig (ed.), Routledge Encyclopedia of Philosophy 4 (London-New York, 1998), 647-654.
3. T Lévy, Hebrew mathematics in the middle ages : an assessment, in Tradition, transmission, transformation, Norman, OK, 1992/1993 (Leiden, 1996), 71-88.
4. B R Goldstein, Astronomy and astrology in the works of Abraham ibn Ezra, Arabic Sci. Philos. 6 (1) (1996), 3, 5, 9-21.
5. B Hughes, Problem-solving by Ajjub al-Basri, an early algebraist, J. Hist. Arabic Sci. 10 (1-2) (1994), 31-39; 150.
6. D E Smith and Y Ginsburg, Rabbi Ben Ezra and the Hindu-Arabic problem, Amer. Math. Monthly 25 (1918), 99-108.