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Israeli, Isaac ben Joseph


ISRAELI, ISAAC BEN JOSEPH (first half of the 14th century), Spanish astronomer who worked in Toledo. Israeli is best known for his book Yesod Olam ("The Foundation of the World") written in 1310, which was considered the most important contribution to Hebrew literature in this field. It dealt with the geometrical problems of the earth in the Ptolemaic system of the universe as revised by al-Biṭsūjī, the seasons, etc., and included astronomical tables. The high esteem in which this book was held over several centuries led to an edition in 1777 being published in Berlin by Jacob Shklover, and a more complete edition, with a preface by David Cassel, was produced in Berlin (1846–48) by B. Goldberg and L. Rosenkranz. There are also commentaries on this work by Isaac *Alḥadib, Judah *Bassan, and Elijah *Mizraḥi. An abridged version in Arabic was written by the author's son, Joseph Israeli b. Isaac, a Hebrew translation of which (under the title Kiẓẓur Yesod Olam) still exists. Isaac Israeli is also the author of two other books, still extant in manuscripts, Sha'ar ha-Shamayim and Sha'ar ha-Millu'im.


Steinschneider, Arab Lit, 164; idem, Die Mathematik bei den Juden (1897), 39; Waxman, Literature, 2 (19602), 320–1; G. Sarton, Introduction to the History of Science, 3 (1947–48), 691–2, includes bibliography; W.M. Feldman, Rabbinical Mathematics and Astronomy (1931), 111.

[Arthur Beer]

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