We have only indirect information about Isaac Israeli’s life. The main sources are an Arab Andalusian biographer active in the second half of the tenth century, Abu DawUd ibn Giulgiul, in his Generations of the Physicians, and, in the mid-eleventh century, Sa‘id of Toledo, in his Generations of the Nations. Althougli the exact dates of his life remain unclear, we tend to assume that Isaac Israeli lived between 850 and 950 CE c. (‘‘an age of over a hundred’’, as we read in the biography by Giulgiul). He was a Jewish eye doctor born in Egypt, who emigrated to Qayrawan (in Tunisia) and entered the service of the local emir, Ziyadat Allah, and then his successor, ‘Ubayd Allah (founder of the Fatimid Ishmaelite dynasty), as their doctor.
Likewise, we still know little of how Israeli’s philosophical formation came about. However, the influence of al-Kindl’s original writings, as well as those of his circle, especially a Neoplatonic Arabic source of The Theology of Aristotle (the so-called ‘‘Ibn Hasday’s Neoplatonist’’), is undoubted: in Israeli there is brasically the same synthesis as found earlier in al-Kindl’s school between Platonic, Aristotelian, and strictly theological elements.
Originally written in Arabic, Israeli’s treatises can be divided into two categories, which had different impacts. The medical treatises - of which are extant the Book of Foodstuffs and Drugs, the Book of Fevers, and the Book of Urine - were very popular throughout the Middle Ages in the Jewish world, as well as in Islamic and Christian circles. Recognizing their value, Israeli himself is supposed to have said that his memory would survive better through these books than through his progeny.
Israeli’s reputation as a philosopher, on the other hand, was less widespread: Jewish philosophers made limited use of his philosophical writings, perhaps because in a well-known letter to Samuel ibn Tibbon (in which a veritable ‘‘canon’’ of the auctoritates of Jewish thought was established), Maimonides held that he was ‘‘only a doctor.’’ Nevertheless, Israeli probably redacted his philosophical treatises just in order to divulge Graeco-Arab doctrines amongst the Jewish public. The following treatises are conserved:
• The Kitab al-Hudud, the Book of Definitions, extant
Both in an incomplete copy of the original Arabic text,
And, in a complete version, in medieval Latin and
Hebrew translations (transcribed, respectively, by
Gerard of Cremona and Nissim ben Shelomoh), is a kind of philosophical dictionary that collects 57 terms from epistemology, logic, metaphysics, psychology and theology. What is striking at this regard is that the work circulated in the Latin West as the ultimate source of the famous veritas est adaequatio rei et intellectus, of which Israeli did not make any mention.
• The Kitab al-Giawahir, the Book of Substances, of which large fragments of the Arabic text are extant, is a cosmological-metaphysical treatise inspired by Aristotle’s Theology.
• Sefer ha-ruah we ha-nefesh, the Book on the Spirit and the Soul, preserved in two Hebrew versions and only in a fragment of the Arabic original, is full of biblical references, as it combines philosophical doctrines of the soul with Jewish scriptural proof (regarding the belief in rewards and punishments of the soul).
• Kitab al-Ustuqsat, the Book on the Elements, which like most of the other philosophical works exists in Hebrew and Latin translations, is a treatise on the quality and quantity of the elements, evidently based on Aristotle.
• Pereq ha-yesodot, the Chapter on the Elements, of which a single Hebrew manuscript exists (at the Biblioteca Comunale of Mantua) was once erroneously ascribed to Aristotle.
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