Isaac al-Isrā’īlī

855–932

Isaac ben Solomon al-Isrā’īlī, a physician and philosopher, was born in Egypt but spent most of his career in Qayrawān, Tunisia, where he was court physician for both the Aghlabids and the Fātimids. An early Jewish Neoplatonist, al-Isrā’īlī wrote several philosophical works. He held that the universe existed through a process of divine emanation, although unlike some Neoplatonists, he allowed that the divine will played a role in it. His primary student in philosophy was Dunash Ibn Tamīm (ca. 890–ca. 956), and he also corresponded with Se‘adya Ga’on (882–942) on philosophical matters. Al-Isrā’īlī was an accomplished medical author; his extant works include monographs on uroscopy, dietary regimens, and fevers. Some of his works were translated into Latin and other languages, and two became part of the medieval Latin medical curriculum. He never married and was childless, reportedly quipping that his book would survive better than any children.

Content by Isaac al-Isrā’īlī

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The Book of Definitions and Descriptions

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The following is an instance: (1) If someone inquires about man whether he exists, the answer must always be “yes,” because man has reality, and what has reality has being, and what has being has no…

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The Book of Elements

Kitāb al-usṭuquṣṣāt (The Book of Elements), Chapter 2
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[ . . . ] One who is ruled by the animal soul will be ignorant, confused, daring, arrogant, eager to kill and to avenge himself, shedding blood, and sexually unrestricted. His character…

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The Book of Fevers

Kitāb al-ḥummayāt (The Book of Fevers), Chapter 2 (selections)
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The one-day fever is special for five properties: a property which distinguishes it only from hectic fever; a property which distinguishes it from Tritaios—that is tertian fever; three properties…

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The Book on Spirit and Soul

Kitāb fī l-rūḥ wa-’l-nafs (The Book on Spirit and Soul), 1-3, 7-9, 15
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The Book on Spirit and Soul and the Difference between the Two, compiled by Rabbi Isaac, the Son of Solomon, known as the Israelite, the Physician, may his Soul rest in Peace Isaac, the son of Solomon…

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The Book of Substances

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[The light of “nature”] is the least bright and that farthest removed from spirituality, because it is at the farthest distance from the true light and pure brilliance, as it merely receives its light…

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The Book of Urine

Kitāb al-bawl (The Book of Urine), Chapter 5
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[As Hippocrates affirmed in his letters:] If the digestion increases, the urine necessarily diminishes; and vice versa, if the urine increases, the digestion must diminish. Urine [emitted]…

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Admonition to the Physicians

Musar ha-rof’im (Admonition to the Physicians), 1, 3, 511, 13, 20-21, 30, 37-39, 47-48
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1. Since it is the nature of living creatures to seek their sustenance and to concern themselves with those things that maintain their being; so, too, is man, whose image is the image of God…