Isaac ibn al-Ahdab

Itzḥak ben Shlomo ibn al-Aḥdab (or ibn al-Ḥadib) ben Tzaddiq ha-Sefardi (Hebrew: יצחק בן שלמה בן צדיק אלאחדב הספרדי, c. 1350 – c. 1426) was a Jewish mathematician, astronomer, and poet.[1]

Ibn al-Aḥdab was born in Castile to a prominent Jewish family. He was a student of Judah ben Asher II, the great-grandson of Asher ben Yeḥiel of Cologne, who was killed in the anti-Jewish massacres of 1391. By 1396 Ibn al-Aḥdab had fled Spain and was in Sicily, where he lived (in Syracuse and Palermo) until his death around 1426.[2]

Work

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He studied the algebra of Maghrebi mathematician Ibn al-Bannā and published The Epistle of the Number, a translation and detailed commentary on Ibn al-Bannā's 13th century treatise Talḵīṣ ʿAmal al-Ḥisāb ("A summary of the operations of calculation").[3] The work is notable in being the first known Hebrew-language treatise to include extensive algebraic theories and operations.[4][5]

His astronomical works include Oraḥ selulah (Upraised Path), a set of tables in Hebrew for conjunctions and oppositions of the Sun and the Moon,[6] Keli Ḥemdah (Precious Instrument), which describes a unique equatorium of his own invention, functioning on the Ptolemaic theory of epicycles,[7] and Keli Memutsa (Intermediate Instrument), which describes another unique instrument of his own design, a combination astrolabe-quadrant.[7] Bernard R. Goldstein published a partial translation of Keli Ḥemdah in 1987.[7] Oraḥ selulah survives in 25 MSS, Keli Ḥemdah in 15 MSS, and Keli Memutsa in 1 MS.[8]

He is the author of a commentary on the Passover Haggadah, titled Pesach Doros (Passover of later generations) and printed by Mekhon Bet Aharon ṿe-Yiśraʼel in 2000.[8]

Leshon ha-Zahav (Golden Language), an explication of the names for units and measurements found in the Hebrew Bible.[8]

He is probably the author of a commentary on Maimonides' Laws of the Sanctification of the Month, found in the same MS as Leshon ha-Zahav with no author given.[8]

He also wrote songs, published as Shirei Rabbeinu Itzḥak ben Shlomo ibn al-Aḥdab (1987). He is known to have composed a work called Shir ha-Shirim, but it has not survived.[8]

References

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  1. ^ Raanan, Ora, ed. (1988). The Poems of Iṣḥak ben Shlomo Al-Aḥdab (in Hebrew). Lod: Mekhon Haberman le-meḥḳere sifrut.
  2. ^ Steinschneider, M. (1964). Mathematik bei den Juden (in German) (2 ed.). Hildensheim. p. 168.
  3. ^ Katz, Victor (2016). "The Mathematical Cultures of Medieval Europe". History and Pedagogy of Mathematics.
  4. ^ Wartenberg, Ilana (2015). The epistle of the number, by Ibn al-Ahdab. Perspectives on Society and Culture. Piscataway: Gorgias Press. ISBN 978-1-4632-0417-4.
  5. ^ Reif, Stefan C. (1997). Hebrew manuscripts at Cambridge University Library: a description and introduction. Vol. 52. Cambridge University Press. ISBN 978-0521583398.
  6. ^ Goldstein, Bernard R.; Chabás, José (2006). "Isaac ibn al-Ḥadib and Flavius Mithridates: The Diffusion of an Iberian Astronomical Tradition in the Late Middle Ages". Journal for the History of Astronomy. 37 (127): 147–172. Bibcode:2006JHA....37..147G. doi:10.1177/002182860603700202. ISSN 0021-8286. S2CID 220913612.
  7. ^ a b c Goldstein, Bernard R. (1987). "Descriptions of Astronomical Instruments in Hebrew". Annals of the New York Academy of Sciences. 500 (1): 105–141. Bibcode:1987NYASA.500..105G. doi:10.1111/j.1749-6632.1987.tb37198.x. ISSN 1749-6632. S2CID 84990297.
  8. ^ a b c d e "HebrewBooks.org Sefer Detail: הגדה של פסח - פסח דורות -- אלאחדב, יצחק בן שלמה". hebrewbooks.org. Retrieved 2021-03-19.
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