Isaac Israeli

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ISRAELI, ISAAC BEN SOLOMON (c. 855-c. 955), physician and philosopher. Born in *Egypt, Israeli emigrated at about the age of 50 to *Kairouan, capital of the *Maghreb, where ʿUbayd Allāh al-Mahdī, founder of the Fatimid dynasty, appointed him court physician. His renown among his fellow Jews is attested by the fact that *Saadiah Gaon, while still in Egypt, addressed numerous letters to him, consulting him on philosophical and scientific matters. He remained unmarried and is quoted as having referred to his books as more likely to keep his memory alive than children would.

Philosophical Writings

Of Israeli's philosophical writings, the Kitāb al-Ḥudūd (Sefer ha-Gevulim, "Book of Definitions") is the best known. It was popular among the Latin schoolmen, who knew it in two versions, a Latin translation of the Arabic original by Gerard of Cremona, and an anonymous abridged Latin text (both edited by J.T. Muckle in Archives d'histoire doctrinale et littéraire du moyen âge, 12–13 (1937–38), 299ff.). Medieval Jewish writers, too, were familiar with the work. Moses *Ibn Ezra reproduces a few passages from it without naming the source in his Kitāb al-Ḥadīqa ("Book of the Garden"), as is most probably also the case with the 11th-century Ghāyat al-Ḥakīm ("Aim of the Wise"), known among the Latin schoolmen as Picatrix, by a Muslim author in Spain who seems to have used Israeli's work. Isaac ibn *Laṭīfy, Abraham*Ibn Ḥasdai, and Isaac de Lattes also mention the book. *Maimonides, in his letter to Samuel ibn Tibbon, lists it among some Neoplatonic treatises described by him as of little merit, whereas Shem Tov ibn *Falaquera remarks: "The books of Isaac Israeli are most useful" (Sefer ha-Mevakkesh). The Arabic original of the work was translated into Hebrew twice. Nissim b. Solomon's version was first published by H. Hirschfeld (in: Festschrift… Moritz Steinschneiders (1896), Heb. sect. 131–41). Fragments of the second Hebrew version were discovered by A. Borosov and edited by A. Altmann (jss, 2 (1957), 232–42). The book offers 56 definitions. It opens with an account (based on al-*Kindī) of *Aristotle's four types of inquiry (whether, what, which, why), and an elaboration of al-Kindī's definitions of philosophy. Israeli's dependence on al-Kindī was first noticed by S.M. Stern. There follow definitions of wisdom, intellect, soul, the celestial sphere, the vital spirit, and nature, which reflect the influence of a Neoplatonic pseudepigraphon (ascribed to Aristotle) that is traceable even more clearly in Israeli's other writings, and other definitions, most of them very brief. Israeli's Kitāb al-Jawāhir ("Book of Substances") has survived only in fragments of the original Arabic, discovered by A. Borisov and edited by S.M. Stern (jss, 7 (1956), 13–29). The Sefer ha-Ru'aḥ ve-ha-Nefesh ("Treatise on Spirit and Soul"), which may have formed part of a larger work (possibly an exegetical treatise on "Let the waters bring forth abundantly," and is extant only in Hebrew, was published by M. Steinschneider (in Ha-Karmel (1871), 400–5). In both works Israeli develops his doctrine of emanation which is derived from the Neoplatonic source mentioned above. A clue to this source is found in another treatise attributed to Aristotle, the Sha'ar ha-Yesodot le-Aristo ("Chapter on the Elements by Aristotle"), preserved in a Hebrew Mantua manuscript, but which, following a suggestion by G. Scholem, A. Altmann has established to be a work by Israeli. It incorporates the previously mentioned pseudo-Aristotelian treatise, and refers to its source in the opening sentence ("Aristotle … said"). In his edition of the Mantua text (jss, 7 (1956), 31–57), Altmann showed that Israeli's metaphysical doctrine throughout his writings is decisively influenced by this source, and he listed a number of parallel texts in other writings (partly already noticed by Scholem and J. Guttmann), which enhanced the significance of the discovery of that source. The relationship between Israeli's source on the one hand, and the parallel texts in Abraham ibn Ḥasdai′s Ben ha-Melekh ve-ha-Nazir and in the long version of the Theology of Aristotle (discovered by Borisov) on the other, has been investigated by S.M. Stern (see A. Altmann and S.M. Stern, Isaac Israeli, A Neoplatonic Philosopher of the Early Tenth Century (1958), 95–105, 114–7, and Stern's article in: Oriens, 13–14 (1961), 58–120). The conclusion reached by Stern is that there existed a Neoplatonic treatise (termed by him "Ibn Ḥasdai's neoplatonist") which served as a source for the anonymous author of the long version of the Theology of Aristotle, Israeli, and Ibn Ḥasdai. A further treatise by Israeli, and the most extensive in scope, is his Kitāb al-Ustuquṣṣāt ("Book on the Elements"), of which there is a Latin version by Gerard of Cremona (printed in Omnia Opera Ysaac) and two Hebrew translations, one by Abraham ibn Ḥasdai (Sefer Yesodot, edited by S. Fried, 1900), and one contained in a Munich manuscript which may have been made by Moses ibn Tibbon. An excerpt from this work and the full texts of all the other treatises by Israeli hitherto mentioned were published in English translation with comments in Altmann-Stern's Isaac Israeli.

His Philosophy

The philosophical doctrine of Israeli describes the various stages of being as a series of emanations from the intellect (Plotinus' Noûs), while the intellect itself is constituted by the union of first matter and first form (the latter also called "wisdom"), which are "created" by the power and will of God. Israeli thus upholds the notion of creatio ex nihilo in the case of the first three hypostases, while adopting the Plotinian concept of emanation for the rest. Both the long version of the Theology and Ibn Ḥasdai use a similar phraseology, due no doubt to their common source. The interposition of first matter and first form between God and the intellect is likewise derived from the peculiar variant of Neoplatonic doctrine represented by Israeli's source, and is reflected also in the parallel texts. A somewhat similar interposition occurs in the pseudo-Empedoclean scheme known from the Hebrew fragments of the "Five Substances" (ed. by D. Kaufmann, in: Studien ueber Salomon Ibn Gabirol, 1899) where, however, spiritual matter alone intervenes between God and the intellect. From the intellect, three souls (rational, animal, and vegetative) and the celestial sphere (also called "nature") emanate. The process of emanation is, following Plotinus, sometimes described as a radiance, "like the light of the sun, which emanates from its essence and substantiality," but is also viewed as a casting of shadows by the light and as the coming-to-be of progressively denser substances out of these shadows. The celestial sphere is the last of the "simple substances" emanating from the intellect, and holds an intermediate position between the higher world and the sensible world. From the motion of the celestial sphere the four elements come into being, and from them, in turn, arise the composite substances of the sublunar bodies. Man's soul, caught in the embrace of the "shells" and "darkness" of the coarse sensible world, is destined to pursue an upward path leading to union with the supernal light of wisdom. Like al-Kindī and the Ikhwān al-ṣafāʾ (*Brethren of Sincerity), Israeli adopts Proclus' theory of the three stages of purification, illumination, and union. The bliss of the highest stage is, in Israeli's view, tantamount to the bliss of paradise. In this way he links traditional Jewish eschatology with Neoplatonic mysticism. He interprets the notion of hell in terms of the impure soul's inability to penetrate beyond the sphere; it is doomed to remain beneath the sphere and to be consumed by its fire. In his concept of prophecy (treated in his Book on the Elements and in the commentary to the Sefer Yeẓirah of his disciple, *Dunash ibn Tamīm, who reflects his master's view), Israeli distinguishes between three forms: that of a created voice (kol); of spirit (ru'aḥ), including vision (ḥazon); and of speech (dibbur), which designates union with the supernal light and represents the highest rank. The case of Moses is described in terms of this highest stage. The function of prophecy is, however, conceived also in terms of spiritual guidance of the multitude of men, for which reason the divine truths must be couched in imaginative, allegorical form. Israeli's influence on the Neoplatonic trend in medieval Jewish philosophy must not be underrated. He is the father of Jewish Neoplatonism, and his traces can be found in such philosophers as Solomon ibn *Gabirol and Joseph ibn *Ẓaddik. The Gerona school of Jewish mysticism is likewise indebted to him. The Mantua text of Israeli's Book on the Elements is quoted in *Azriel of Gerona's commentary on the Aggadot.

Medical Works

Israeli has been classed among the great physicians of the early Middle Ages. From 875 to 904 he apparently was a successful eye doctor near Cairo. His medical works were translated (or adapted) by Constantine the African (1087) from the Arabic into Latin, and were thus introduced to Europe and included in the Salerno school. Innumerable manuscripts in Arabic, Latin, and Hebrew by various translators testify to their popularity. Among Israeli's medical and quasi-medical writings are books on urine, fevers, the pulse, drugs, and the abovementioned "Treatise on Spirit and Soul" in a half-medical and half-philosophical treatise, probably part of a commentary on Genesis (all printed in Omnia Opera Isaac, 1515). A work entitled Musar ha-Rofe'im ("Medical Ethics") has also been attributed to Israeli, though his authorship has been doubted by some scholars.

[Alexander Altmann]

Harry A. Wolfson questioned Alexander Altmann's interpretation of Israeli's doctrine of creation in "The Meaning of Ex Nihilo in Isaac Israeli," in: jqr, 50 (1959), 1–12 (reprinted in Wolfson, Studies in the History of Philosophy and Religion, 1(1973), 222–33) and was answered by Altmann in "Creation and Emanation in Isaac Israeli: A Reappraisal," in: I. Twersky (ed.), Studies in Medieval Jewish History and Literature (1) (1979), 1–15. See also G. Vajda, in: P.B. Fenton, Le Commentaire sur le Livre de la Création de Dunas ben Tamim de Kairouan (Xe siècle) (2002).

[Daniel J. Lasker (2nd ed.)]


J. Guttmann, Die philosophischen Lehren des Isaak b. Salomon Israeli (1911); idem, in: mgwj, 69 (1919), 156–64; Altmann, in: Tarbiz, 27 (1958), 501–7; Plessner, in: ks, 35 (1960), 457–9; H. Friedenwald, Jews and Medicine, 3 (19672), 86–88, with list of medical works and bibl.

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Son of Solomon, Jewish physician and philosopher, also known as Isaac Judaeus; d. c. 932. Isaac was a native of Egypt who emigrated to Qayrawān (in modern Tunisia) about 907 and became a physician to the Fatimid Caliph Ubayd Allah al-Mahdi. According to some authorities he died shortly before 932, but other accounts (of doubtful authority) imply that he was alive at later dates. His medical treatises, e.g., the Book of Fevers, the Book of Urine, the Book of Foodstuffs and Drugs, all written in Arabic, were long considered classics, and translated into Hebrew and Latin, giving their author fame among Muslims, Jews, and Christians. His medical reputation was somewhat overshadowed in the West by his Latin translator, constantine the african. Constantine's work, completed by 1087, best described as a paraphrase of Isaac's writings, received wide currency in medieval schools of medicine, as attested by surviving MSS.

As a philosopher, Isaac's inspiration was mainly Neoplatonic. The writings of the Muslim philosopher al-kindĪ abŪ yŪsuf and a Neoplatonic treatise ascribed to Aristotle (Ibn Hasday's Neoplatonist ) were the main influences on his philosophy. His writings in this field assumed the form of short treatises in Arabic: the Book of Definitions (Latin translation by Gerard of Cremona, two Hebrew translations); the Book of Substances, extant in fragmentary form; the Book on Spirit and Soul, in which Neoplatonic psychology is given Biblical foundation; a text known as Chapter on the Elements (in Hebrew translation only); and a somewhat longer treatise, Book of the Elements (extant in a Latin version by Gerard of Cremona, and two Hebrew versions). Whereas among the Muslim philosophers Israeli had no influence, his work seems to have been generally known among the Jewish Neoplatonists of Spain, although a more strictly Aristotelian philosopher of the rank of maimonides had naturally little sympathy with Israeli's somewhat primitive Neoplatonism. The texts available in Latin were used by schoolmen such as dominic gundisalvi, albert the great, and thomas aquinas.

Bibliography: Omnia Opera Ysaac (Lyons 1515). m. steinschneider, Die hebräischen Übersetzungen des Mittelalters (Berlin 1893); Die arabische Literatur der Juden (Frankfurt A. M.1902). c. brockelmann, Geschichte der arabischen Literatur, 3v. (Leiden 193742). g. sarton, Introduction to the History of Science (Baltimore 192748) v.1. a. altmann and s. m. stern, Isaac Israeli: A Neoplatonic Philosopher of the Early Tenth Century (London 1958). j. schmid, Lexikon für Theologie und Kirche, ed. j. hofer and k. rahner (Freiberg 195765) 5:773.

[s. m. stern]

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Isaac Israeli

(b. Egypt, fl. ninth-tenth century)

medicine, philosophy.

Nothing is known of Isaac Israeli’s early life or his education. A Jewish physician and philosopher, he immigrated to Ifriqiya (now Tunisia) sometime after 900 and became the court physician to the last Aghlabid emir and, after he was ousted, to the Fatimid caliph who succeeded him. Although the date of Israeli’s death is uncertain, there is some ground for placing it about 955.

Of his medical works, the Book on Fevers and the Book on Urine were highly regarded textbooks. An edition of the Arabic original of the Book on Fevers is in preparation; a comparison of Constantine the African’s Latin version with the original has shown it to be more a condensed paraphrase than a literal translation. Constantine also prepared Latin versions of the Book on Urine and the Book on Foodstuffs and Drugs. There are also Hebrew translations of the medical works.

Israeli’s philosophy, purely Neoplatonic in character, is mainly based on a treatise in Arabic that, like other similar texts, was attributed to Aristotle, and on the writings of the Muslim philosopher al-Kindī.His themes were the process of emanation, the elements, and the soul and its return to the upper world. He wrote a number of short treatises on philosophy, of which the Book of Definitions and Descriptions, largely based on al-Kindi, was widely used by the Schoolmen in a Latin version by the twelfth-century translator Gerard of Cremona. Whereas the Book of Substances, of which only part is extant, is a kind of commentary on the pseudo-Aristotelian text, the Book on Spirit and Soul supports its doctrines with biblical quotations. In addition, there is a treatise called Chapter on the Elements, extant only in the Hebrew version, and a lengthier Book on the Elements, which exists in Latin and Hebrew editions, the former by Gerard of Cremona.


There is a biographical note in A. Altmann and S. M. Stern, Isaac Israeli. A Neoplatonic Philosopher of the Early Tenth Century (Oxford, 1958), which also contains references to the editions of the philosophical treatises, the English translation, with commentary, of the philosophical treatises, and a systematic exposition of Israeli’s philosophy that supersedes J. Guttmann, Die philosophischen Lehren des Isaak b. Solomon Israeli (Münster, 1911). Constantine the African’s Latin versions were printed in Opera omnia Ysaac (Lyons, 1515). The relation between the Arabic original of the Book on Fevers and the Latin (as well as the Castilian) version in studied by J. D. Latham is Journal of Semitic Studies (1969).

Among the bibliographic references in Altmann and Stern, the most important are M. Steinschneider, Die hebräischen Übersetzungen des Mittelalters (Berlin, 1893), sec. 479; and Die arabische Literatur der Juden (Frankfurt, 1902), sec. 28; and G. Sarton, Introduction to the History of Science (Baltimore, 1927), pp. 639 ff.

S. M. Stern

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Isaac Israeli


Jewish Egyptian physician and philosopher who wrote on a number of subjects and greatly influenced European medicine. The dates of Isaac's life are uncertain—he could have been born as late as 855, and died as late as 955—but it is known that he lived to be about 100 years old. During his long career, he served the Fatimid caliphs in Egypt and wrote eight medical works on topics that included fevers, urine, pharmacology, ophthalmology, and various diseases and treatments. Translated by Constantine the African (c. 1020-1087), these writings would have a great impact in Western Europe. As a philosopher, Isaac is considered the father of Jewish Neoplatonism in the Middle Ages.

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Israeli, Isaac ben Solomon (c.855–955). Jewish philosopher. Israeli was court physician in Kairouan, the capital of the Maghreb. He was the author of Kitāb al-Hudūd (The Book of Definitions) which attempts to define such concepts as the soul, wisdom, the intellect, and nature.