Medieval Arabic-Islamic Philosophy: The Falsafa from Al-Farabi to Averroes

Between the ninth and twelfth centuries, while the Latin West knew only fragments of Aristotle, the Islamic world was the great guardian and continuator of Greek philosophy. Falsafa — the Arabic transliteration of the Greek philosophía — names the tradition that received, commented upon, and transformed the legacy of Aristotle and of Neoplatonism, facing the decisive problem of articulating Greek philosophical reason with Qur’anic revelation. Without it there would have been no rediscovery of Aristotle in the West and, to a large extent, no Scholasticism of Thomas Aquinas. This article traces its protagonists — Al-Kindi, Al-Farabi, Avicenna, Al-Ghazali, and Averroes — and the debate that runs through them.

1. The Translation Movement and Al-Kindi

Falsafa is born of an extraordinary cultural undertaking: the translation movement sponsored by the Abbasid caliphate in Baghdad (8th–10th centuries), centered on the so-called House of Wisdom (Bayt al-Ḥikma). Greek works of philosophy, medicine, mathematics, and astronomy were rendered into Arabic, often by way of Syriac. This effort placed at the disposal of Islamic thinkers the Aristotelian corpus, the late commentators, and Neoplatonic texts.

Al-Kindi (c. 801–c. 873), called “the Philosopher of the Arabs” (faylasūf al-ʿArab), was the first major philosopher of this tradition. In On First Philosophy (Fī al-Falsafa al-Ūlā), he argued that truth is one, whether it comes from the Greeks or from revelation, and that to seek it wherever it lies is the philosopher’s duty. Unlike the later Aristotelians, Al-Kindi defended creation in time and the finitude of the world, in keeping with Islamic theology — anticipating the tension that would divide the falsafa.

2. Al-Farabi, the “Second Teacher”

Al-Farabi (c. 872–c. 950), born in the region of Farab (modern Kazakhstan), was called by tradition “the Second Teacher” (al-Muʿallim al-Thānī) — the first being Aristotle. He worked mainly in Baghdad and Aleppo, and his work spans logic, politics, metaphysics, and even music theory.

His emanationist cosmology adapts Plotinus’s Neoplatonism to Ptolemaic astronomy: from the First (the One, identified with God) emanate ten separate intellects, each tied to a celestial sphere; from the tenth — the Active Intellect — emanate the sublunary world and the illumination of the human intellect. In his theory of the intellect, Al-Farabi distinguishes the degrees by which the mind passes from pure potency to the “acquired intellect” in contact with the Active Intellect — a scheme decisive for Avicenna and for Scholasticism.

In political philosophy, his Virtuous City (Al-Madīna al-Fāḍila) takes up Plato: the ideal ruler is at once philosopher and prophet, able both to grasp the truth and to communicate it to the many through images and symbols — a function Al-Farabi assigns to religion. In The Harmony of Plato and Aristotle, he held — influentially but very controversially — that the two masters converged on essentials.

3. Avicenna (Ibn Sīnā): The Metaphysical Summit

Avicenna (980–1037), born near Bukhara, in Persian-speaking Central Asia, is the greatest philosopher of the medieval Islamic world. A prodigious physician (his Canon of Medicine served as a European textbook for centuries) and the author of a vast philosophical encyclopedia, the Book of Healing, he left to metaphysics a distinction that would change Western thought: the separation between essence and existence.

In any being we can ask what it is (its essence) and whether it is (its existence) — and the two do not coincide: the essence of a horse says nothing about whether horses exist. From this Avicenna draws his central thesis: in creatures, existence is contingent (they could fail to exist); only in God do essence and existence coincide. God is the Necessary Being (wājib al-wujūd), that which cannot not be and from which everything else, “possible in itself,” receives existence. Like Al-Farabi, he explains the origin of the world through a cascade of ten intelligences emanating from God.

Famous is his “flying man” argument: imagine a man created fully grown, suspended in the air, with no sensation whatever — he would still be aware that he exists, proof that the soul knows itself independently of the body (an intuition anticipating Descartes’s cogito). Avicennian metaphysics was decisive for Thomas Aquinas, Duns Scotus, and all of Latin Scholasticism.

4. Al-Ghazali: The Critique of the Philosophers

The synthesis of the falsafa met its most formidable objection in Al-Ghazali (c. 1056–1111), theologian, jurist, and Sufi mystic, latinized as Algazel. In The Incoherence of the Philosophers (Tahāfut al-Falāsifa), he subjected the falsafa — chiefly Avicenna and Al-Farabi — to a devastating examination of twenty theses, declaring three of them incompatible with faith to the point of constituting unbelief (kufr): the eternity of the world, the thesis that God knows only universals (and not particulars), and the denial of bodily resurrection.

Philosophically, his sharpest weapon is the critique of necessary causality: when we see cotton burn on contact with fire, we perceive no necessary connection, only a habitual conjunction. The real cause of every effect is God — an occasionalist position that anticipates, by several centuries, Hume’s arguments about induction. In his spiritual autobiography, Deliverance from Error (al-Munqidh min al-Ḍalāl), he recounts the crisis of doubt that led him from rationalism to mystical experience as the path to certainty.

5. Averroes (Ibn Rushd): The Commentator

The response came from the Islamic West. Averroes (1126–1198), born in Córdoba at the height of Al-Andalus, a judge and physician in the service of the Almohad caliphs, was known in medieval Europe simply as “the Commentator”: his meticulous commentaries on nearly all of Aristotle’s work were, for centuries, the gateway to the Stagirite for Latins and Jews alike.

Against Al-Ghazali, Averroes wrote The Incoherence of the Incoherence (Tahāfut al-Tahāfut), arguing that philosophy and revelation do not contradict one another: they are two paths to the same truth — one demonstrative, addressed to the learned, the other persuasive and symbolic, addressed to the many. When the revealed text seems to clash with demonstrative reason, allegorical interpretation (taʾwīl) is in order. Hence his thesis of the autonomy of philosophy, with a domain of its own alongside theology.

Beware a frequent error: Averroes did not hold the so-called “double truth” (the idea that something could be true in philosophy and false in theology, or vice versa). That doctrine was attributed — probably unfairly — to the Latin Averroists (such as Siger of Brabant) and condemned in Paris in 1277. For Averroes himself, truth is one.

His most controversial theses were the eternity of the world and the doctrine of the unicity of the intellect: there would be a single material intellect common to all humanity, in which individuals participate — which seemed to deny the personal immortality of the soul. Transplanted to the University of Paris, they provoked the forceful reaction of Thomas Aquinas (On the Unity of the Intellect against the Averroists) and became one of the great debates of Scholasticism.

6. Legacy: Transmission and the Question of “Decline”

Falsafa was not a mere link of transmission but a creative philosophical tradition. Its impact on the West was immense: through the Arabic-Latin translations made in Toledo and Sicily (12th–13th centuries), Aristotle and his Islamic commentators reached the European universities and shaped Scholasticism. The same tradition nourished medieval Jewish philosophy — Maimonides (1138–1204), in Córdoba and Cairo, wrote his Guide for the Perplexed in direct dialogue with Al-Farabi and Avicenna.

It is often claimed that Al-Ghazali’s critique brought about the “decline” of philosophy in Islam. The thesis is now contested: in the Persian and Shi’a East, falsafa continued in transformed shape — in the philosophy of illumination (ishrāq) of Suhrawardī (1154–1191) and, centuries later, in the synthesis of Mullā Ṣadrā (c. 1571–1640). What changed was less its vitality than its form: philosophy migrated into theology and mysticism rather than vanishing.

Essential Readings

• Al-Kindi, On First Philosophy (Fī al-Falsafa al-Ūlā).
• Al-Farabi, The Virtuous City (Al-Madīna al-Fāḍila); Treatise on the Intellect.
• Avicenna, The Book of Healing (Kitāb al-Shifāʾ), metaphysics section; Canon of Medicine.
• Al-Ghazali, The Incoherence of the Philosophers (Tahāfut al-Falāsifa); Deliverance from Error.
• Averroes, The Incoherence of the Incoherence (Tahāfut al-Tahāfut); The Decisive Treatise (Faṣl al-Maqāl).
• Maimonides, Guide for the Perplexed.

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