al-Kindī

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Abū Yūsuf Yaʿqūb ibn Isḥāq al-Kindī (c. 801–873) was the first major philosopher to write in Arabic, a polymath of Abbasid Baghdad remembered in the tradition as faylasūf al-ʿArab, the Philosopher of the Arabs. The title was partly literal: he was the rare figure of Arab tribal descent — from the Kinda, a princely lineage of the south that gave him his name — in a learned world otherwise dominated by Persians and converts. His father governed Kufa for the caliphs; the son was schooled in Basra and then drawn to Baghdad, the new round city on the Tigris, in the decades when the caliphate was pouring its wealth into the recovery of Greek learning.

The translation movement and the circle

He worked at the center of that recovery — the great translation movement, the project by which Greek philosophy and science were carried into Arabic under caliphal patronage during the Islamic Golden Age. Al-Kindī did not himself master Greek. What he did instead was organize: he gathered, directed, and revised the work of translators, and around him formed a workshop that modern scholarship calls the Circle of al-Kindī. Out of it came some of the texts that would shape philosophy in Arabic for centuries — among them the so-called Theology of Aristotle (Uthūlūjiyā), in fact a paraphrase of the Enneads of Plotinus, and an Arabic Metaphysics of Aristotle. That a Neoplatonic text could travel under Aristotle’s name was no accident of sloppiness; it expressed a conviction the circle worked to make true, that the Greek philosophers spoke, beneath their disagreements, with one voice.

From this base al-Kindī built a body of writing of extraordinary range. Ibn al-Nadīm’s Fihrist, the tenth-century book-catalog of Baghdad, credits him with on the order of two hundred and ninety treatises — on metaphysics, logic, mathematics, astronomy, meteorology, optics, music, medicine, pharmacology, and the deciphering of secret writing. Most are lost in the original; a portion survives in Arabic, and a further portion only in the Latin into which they were rendered in twelfth-century Spain. He composed a treatise On the Use of Indian Arithmetic that helped carry the decimal place-value system westward; a pharmacology, the De gradibus of the Latins, that applied a mathematics of proportion to the strength of compound drugs; and works on perspective and the propagation of light, the De aspectibus, that fed directly into the optics of the Latin Middle Ages.

One of his treatises stands alone in its afterlife. In the Risāla fī Istikhrāj al-Muʿammā, on the deciphering of coded messages, al-Kindī set down what is the oldest surviving description of cryptanalysis by frequency analysis — the technique of breaking a substitution cipher by counting how often each letter recurs in a long sample of ordinary text and matching the commonest cipher-signs to the commonest letters of the language. The insight may have grown from the close counting of words and letters that scholars brought to the Qurʾān; turned on a cipher, it became the most fundamental advance in codebreaking before the twentieth century. The manuscript itself was not recovered and published until the late twentieth century, from an Ottoman archive in Istanbul.

Greek wisdom and the Qurʾanic God

His philosophical ambition was to show that the wisdom of the Greeks and the truths of Islam were one — an argument he pressed against theologians who held that revelation needed no help from pagan reason, and that the foreign sciences were a danger to the faith. Al-Kindī answered that truth has no nationality; one must accept it gratefully from whatever source carries it, even from peoples remote in time and tongue. This was the founding gesture of falsafa, philosophy in the Greek line conducted in Arabic and within Islam, and it is why he stands at the head of that lineage rather than merely within it.

The philosophy he assembled was a particular blend. He took Aristotle as the framework — the categories, the four causes, the analysis of the soul and the intellect — but read him through the late Greek commentators, so that into his account of the cosmos flowed Neoplatonic material. Above all there flowed the doctrine of a single source from which all things proceed by emanation, which al-Kindī aligned with the Qurʾanic God as the true One, the cause of all unity in things that are otherwise many. His God is austere to the point of namelessness: because every predicate divides a thing into the named and the named-of, and so introduces multiplicity, the One that is the cause of all oneness can bear no predicate proper to creatures and is one in a sense nothing else can share. This is the metaphysics of tawḥīd, the divine unity, given the rigor of a Greek argument — a strand of Islamic Neoplatonism worked out before the great systems that would follow.

The break with Aristotle on the eternity of the world

The same ambition shaped his account of the human person. Following the late Greek reading of Aristotle’s On the Soul, al-Kindī took the rational soul to be an incorporeal substance, kin to the higher world and only lodged in the body; its proper destiny is to ascend, after the body, toward the light of the divine realm. He worked out a theory of the intellect — how the mind passes from bare potential to actual knowing under the action of a separate, always-actual intellect above it — that became a fixed problem for everyone after him, restated and disputed by al-Fārābī and Avicenna in turn. He brought the same temper to feeling as to thought. In a short treatise On the Means of Dispelling Sorrows he argued that grief is the loss of something one loved and cannot keep, and that since the things of this world are by nature impermanent, to set the heart on them is to arrange one’s own suffering; the cure is to value what cannot be taken — a piece of consolation-philosophy in the Stoic and Neoplatonic line, given an Arabic voice. And he held that the order he found in the cosmos was audible as well as visible: his writings on music treat consonance and rhythm as proportion made sensible, the same harmony that governs the spheres sounding in the strings of the lute.

On one question he broke decisively with Aristotle and sided with scripture: the eternity of the world. Aristotle had held the cosmos to be without beginning, turning forever. Al-Kindī argued instead, in his chief surviving work On First Philosophy (Fī al-Falsafa al-Ūlā), that the universe was created in time, that it has an absolute beginning, and that there is therefore a Creator who brought being out of nothing. His proof turned Aristotle’s own commitments against him. A body, Aristotle agreed, cannot be actually infinite; the cosmos is a body of finite magnitude; and time, motion, and the body of the world are bound together so that none can outrun the others. An eternal past would require that an actually infinite series of moments had already elapsed before the present — and an actual infinite, on Aristotle’s own showing, cannot be traversed or completed. So the world cannot be beginningless. In pressing this case al-Kindī took up a line of attack first sharpened by the sixth-century Christian Aristotelian John Philoponus of Alexandria, who had used the same instruments to the same end; al-Kindī carried it into Arabic and made the finitude of the created order a philosophical position rather than a mere article of belief.

Eclipse in the East, ascent in the West

Later philosophers in Arabic would build more rigorous and more comprehensive systems and eclipse him. Al-Fārābī, a generation on, recast the relation of philosophy to religion and to the city; Avicenna constructed a metaphysics of necessary and possible being so powerful that it became the frame within which later thinkers argued. Beside them al-Kindī came to look like a first attempt — important, but superseded. Yet his fortunes ran oddly. Within the tradition he had founded his star sank; in the Latin West it rose. Through the translations of Gerard of Cremona and others his optics, pharmacology, and astrological writings entered the European schools, and his name carried weight there for centuries. The Renaissance physician and mathematician Geronimo Cardano ranked him among the greatest minds of the past — a standing in the West that for a long while outran his reputation in the East.

His own end was less serene than his eminence. He had tutored Ahmad, son of the caliph al-Muʿtaṣim, and prospered under that patronage; but under the caliph al-Mutawakkil, amid the rivalries of the scholars and a turn against heterodoxy, he fell from favor. By one account he was beaten, and his library — the Kindiyya — was confiscated and handed to the Banū Mūsā, the brothers who were his rivals in the mathematical sciences; it was restored to him only later, through the intercession of the astronomer Sanad ibn ʿAlī.

On the Stellar Rays

That Latin afterlife rests, more than on any other single thing, on a work of a different kind. A treatise On the Stellar Rays (De radiis), transmitted under al-Kindī’s name and surviving only in Latin, holds that every thing in the heavens and on earth radiates power — that each object pours out rays in every direction, and that the whole of nature is therefore a single web of action in which everything works upon everything else. The stars, vastly the strongest radiators, weave at each instant a configuration of rays unique to that instant and place; and because the things below are knit into the same web, the heavenly pattern conditions what comes to be beneath it. The same doctrine extends to the human word and image: a spoken name, a figure drawn, a thing made and timed to the sky, all emit rays of their own and can be composed so as to draw on the network of forces. Here the treatise touches the architecture of the talisman and of astral magic — not the manner of making one, but the picture of the world that would make such making intelligible.

What that picture supplied was a naturalistic footing. The efficacy of a consecrated object need not be referred to spirits summoned and commanded, with all the suspicion of the demonic that attached to such commerce; it could be referred instead to a cosmos in which cause radiates everywhere, so that the maker is not conjuring an outside power but tuning an instrument to forces already streaming through all things. This is the deep affinity, and the deep difference, between De radiis and the religious astralism of the Sabians of Ḥarrān, for whom the planets were addressed as living powers: the rays-theory keeps the working universe and drains the gods from it. The same logic underwrites devices like the magic square and the wider tradition of Islamic astral and talismanic science, and it sits within the larger current of the Arabic Hermetica, the technical corpus of astral causality and sympathetic correspondence that Abbasid learning gathered under the name of Hermes. Whether al-Kindī wrote De radiis as it now stands is uncertain — the work survives in Latin alone, and the scholarship places it in his circle or pseudonymously soon after rather than securely in his own hand — but under his authority it became one of the founding texts of medieval astral magic, cited by Roger Bacon and others from the thirteenth century onward, and condemned by churchmen for precisely the reach it claimed.

Texts and scholarship

The reconstruction of al-Kindī rests on a small surviving Arabic remnant and a larger Latin one, edited and studied across the last century. The standard critical edition and English translation of his metaphysical and cosmological treatises is Alfred L. Ivry’s Al-Kindī’s Metaphysics: A Translation of Yaʿqūb ibn Isḥāq al-Kindī’s Treatise “On First Philosophy” (State University of New York Press, 1974), which sets the eternity-of-the-world argument beside its Greek sources. The fullest single account of his thought in English is Peter Adamson’s Al-Kindī (Oxford University Press, 2007), condensed in his entry al-Kindi in the Stanford Encyclopedia of Philosophy, which treats the metaphysics of the One, the theory of intellect and soul, and the relation to the kalām theology of the day. The institutional setting — how Greek texts moved into Arabic, and what al-Kindī’s circle did with them — is the subject of Dimitri Gutas’s Greek Thought, Arabic Culture (Routledge, 1998), the standard study of the translation movement.

The disputed De radiis has its own apparatus. The critical Latin edition is Marie-Thérèse d’Alverny and Françoise Hudry, “Al-Kindi, De radiis,” in Archives d’histoire doctrinale et littéraire du Moyen Âge 41 (1974), the text on which all later discussion rests. Its place in the history of magical theory — how the rays-doctrine grounded the talisman in nature rather than in spirits, and how it traveled into the Latin West beside the Picatrix — is laid out in Liana Saif’s chapter Arabic Theories of Astral Magic: The De radiis and the Picatrix, in The Arabic Influences on Early Modern Occult Philosophy (Palgrave Macmillan, 2015). Modern scholarship treats al-Kindī less as a finished system than as a beginning — the point at which philosophy in Arabic first found its vocabulary, and the moment the foreign sciences were claimed for the faith rather than fenced off from it.

What he left was an argument, made before it could be taken for granted, that the inherited learning of the Greeks belonged to Islam as fully as to anyone.

→ Related: Al Farabi · Avicenna · Arabic Falsafa Islamic Philosophy · Astral Talismanic Magic · Islamic Golden Age · Neoplatonism · Islam · Aristotle · The One · Emanation · Islamic Neoplatonism · Talisman · Islamic Astrology Alchemy Astral Magic · Sabian Harranian Astral Religion · Magic Square · Roger Bacon · Arabic Hermetica