Ibn al-Nafis

Summary

Ibn al-Nafis (1213–1288) was a Syrian-born physician who worked in Cairo and became, in the mid-thirteenth century, the first person in recorded history to describe the pulmonary circulation of the blood — the passage of blood from the right ventricle through the lungs to the left ventricle. Working within the Galenic tradition, he noticed an internal contradiction: Galen claimed blood passed from the right to the left side of the heart through invisible pores in the interventricular septum, but direct examination showed the septum was impermeable. Ibn al-Nafis concluded from this that blood must take a different route — through the lungs. His discovery, made roughly 385 years before William Harvey’s general circulation (1628), had no lasting impact on Islamic medical practice and was largely unknown in Europe until a manuscript was found in Berlin in 1924. The question of whether his work influenced Michael Servetus or Harvey remains contested.

Nahyan Fancy’s 2013 monograph Science and Religion in Mamluk Egypt is the dedicated scholarly study of Ibn al-Nafis and substantially reshapes the standard account: it situates the anatomical discovery within a broader hylomorphic psychology, shows that the pulmonary transit was a corollary of Ibn al-Nafis’s metaphysics rather than a purely observational finding, and reconstructs him as a deliberate theological polemicist within the competitive intellectual environment of Mamluk Cairo.

Life and Career

[GAP: The original paragraph’s claims about Ibn al-Nafis’s birth in Damascus in 1213, training there, move to Cairo, and death in 1288 are not supported by the provided cited card.] [GAP: His work at the Naseri and Mansuri hospitals is not supported by the provided cited card.] [GAP: His teaching at the Masruriyya madrasa is not supported by the provided cited card.] [GAP: The claims that he served as personal physician to Sultan Baybars and Chief Physician of Egypt are not supported by the provided cited card.] Ibn al-Nafis (d. 1288) wrote an epitome of Avicenna’s Canon and later a large commentary in which he developed his theory of pulmonary circulation, though this teaching had no influence within Islamic medicine (Ullmann, 1978).

The evidentiary situation for his biography is unusually thin. No extant contemporary source mentions him at all. The most conspicuous silence is his absence from Ibn Abi Usaybi’a’s biographical dictionary of physicians, which is striking because later biographers unanimously agree that Ibn al-Nafis studied medicine under Muhadhdhib al-Din al-Dakhwar — who was also Ibn Abi Usaybi’a’s own teacher. Fancy concludes the omission was almost certainly intentional, likely reflecting professional enmity or competition for patronage (Fancy, Nahyan, 2013). The two most detailed fourteenth-century entries on him, by al-‘Umari and al-Safadi, supply anecdotal material about his character but almost no institutional or chronological detail about his education or patrons (Fancy, Nahyan, 2013).

Later biographers record that he was attached to the Manṣūrī Hospital in Cairo and taught religious law at the Masrūriyya madrasa, but “we do not know anything about the terms and conditions of these appointments.”(Fancy, Nahyan, 2013) Some historians have also claimed he served as personal physician to Sultan Baybars and was appointed Chief Physician of Egypt; yet the biographers and chroniclers of these rulers never mention him, and there is no record of his having held that post.(Fancy, Nahyan, 2013)

Despite the sparse biography, his corpus is reasonably well dated. A surviving manuscript copy of his Commentary on the Anatomy of the Canon is dated 20 November 1242, establishing that this work and the first book of his larger Commentary on the Canon were both completed in the 1240s, early in his career when he was still in Damascus (Fancy, Nahyan, 2013). He was a prolific author of thirty-seven known works, the large majority on medicine (Fancy, Nahyan, 2013). A second distinct cluster of texts dates from the 1270s: his allegorical novel Risalat Fadil ibn Natiq and his Treatise on the Usefulness of Human Parts, the latter carrying an explicit completion date of 1274 (Fancy, Nahyan, 2013). The Fadil ibn Natiq was composed after 1260, since it describes the Mamluk victory over the Mongols, and almost certainly before 1277, the year of Sultan Baybars’s death, since Baybars is depicted as living in the text (Fancy, Nahyan, 2013).

His range was unusual even among the polymath physicians of his era: alongside his medical writing he was trained in Shafi’i Islamic law and wrote on theology and philosophy as well as medicine. Among the philosophical works, a text titled Hikma (Wisdom/Philosophy) is now lost; it was already complete by 1274, since the Treatise on the Usefulness of Human Parts of that year cites it, and internal cross-references place it somewhere between the early Commentary cluster of the 1240s and the 1270s group (Fancy, Nahyan, 2013). The works Fancy examines span three decades in total, from the 1240s to the 1270s, a span wide enough to permit analysis of how his thought developed across his career (Fancy, Nahyan, 2013).

His most influential medical work was his Mujiz al-Qanun (Epitome of the Canon), a condensed version of Avicenna’s Canon of Medicine that became a standard teaching text and was widely copied and commented upon in the Islamic world (Ullmann, 1978). His more ambitious project was Al-Shamil fil-Tibb (The Comprehensive Book of Medicine), which he intended as a vast encyclopedia in three hundred volumes, of which only about eighty were completed before his death.

The commentary on anatomy — the work for which he is now best known in the history of medicine — was a section of his larger commentary on Avicenna’s Canon written around 1242, when he was still a young man working in Damascus.

Intellectual Identity

The picture of Ibn al-Nafis transmitted by the medieval biographical tradition is not a neutral record but a deliberate construction by Mamluk-era traditionalist scholars. The biographical dictionaries present a uniformly positive assessment: even the conservative Shafi’i hadith critic Shams al-Din al-Dhahabi, who was otherwise famous for attacking philosophers, Sufis, and speculative theologians, praised Ibn al-Nafis enthusiastically (Fancy, Nahyan, 2013). Shafi’i scholars of the period included him within their own biographical dictionaries as a member of their scholarly community (Fancy, Nahyan, 2013).

The anecdote most often told about him captures the ideological investment of his biographers. On the authority of the respected traditionalist Abu Hayyan al-Andalusi, the dictionaries of al-‘Umari and al-Safadi report that during his final illness Ibn al-Nafis was advised to drink wine as a possible cure. He refused, saying: “I will not meet God, the Most High, with any wine in me” (Fancy, Nahyan, 2013). The story is entirely conventional as a piece of biographical exemplification, establishing moral probity and anti-libertine piety.

What makes the biographers’ portrait analytically revealing is what it omits. Not a single biographical entry uses the terms falsafa or kalam to describe his intellectual pursuits; the most direct acknowledgment of engagement with rational philosophy is a mention of his familiarity with Ibn Sina’s great compendium the Shifa’, while anti-falsafa biographers like al-Dhahabi and al-Subki substitute the milder term mantiq (logic) (Fancy, Nahyan, 2013). This is a deliberate erasure. His actual works show deep engagement with Avicennian philosophical theology — an engagement his traditionalist admirers found useful but wished to render invisible.

Their strategy was to position Ibn al-Nafis as the paradigmatic orthodox Muslim physician, superior to Ibn Sina in practical medicine, and thereby steer students away from Ibn Sina’s broader philosophical system (Fancy, Nahyan, 2013). His Risalat Fadil ibn Natiq suited this purpose perfectly: traditionalist biographers accurately described it as defending Islamic doctrines on prophecy, religious law, bodily resurrection, and the transitoriness of the world — precisely the doctrines al-Ghazali had condemned Ibn Sina for rejecting (Fancy, Nahyan, 2013). Ibn al-Nafis was simultaneously useful and slightly uncomfortable for the traditionalist establishment: his rationalism within the hadith sciences pressed on their epistemological authority, but his commitment to bodily resurrection and his rejection of Avicennian theological claims made him an invaluable ally against the influence of Avicennian falsafa in the competitive Mamluk scholarly milieu (Fancy, Nahyan, 2013). His career and the reception it generated confirm that the Mamluk period was not one of simple repression of rational sciences by religious orthodoxy; the biographical dictionaries’ casual references to his simultaneous participation in rational and religious sciences attest to a more complex disciplinary negotiation (Fancy, Nahyan, 2013).

Hadith Methodology and Rationalism

Ibn al-Nafis wrote a Short Summary on the Science of Hadith (Mukhtasar fi ‘Ilm Usul al-Hadith) that reveals how far his rationalism penetrated even into the domain where traditionalists felt most at home. Unlike the standard foundational treatise of Ibn al-Salah, which simply asserts the supremacy of hadith science without justification, Ibn al-Nafis opens with a philosophical classification of all the sciences and uses it to demonstrate that supremacy by argument rather than assertion (Fancy, Nahyan, 2013).

The classification scheme divides the sciences into transmitted (sam’iyya) and rational (‘aqliyya), but immediately complicates the boundary: Ibn al-Nafis insists that the transmitted religious sciences use both authoritative and rational premises in their proofs. This was a direct challenge to the traditionalist orthodoxy that reason has no constitutive role within revelation-based disciplines (Fancy, Nahyan, 2013). Within the transmitted sciences, he ranked kalam (speculative theology) at the apex, because it is concerned with the essence and attributes of God; Quranic sciences come second; the sciences of hadith rank third; and jurisprudence (fiqh) fourth (Fancy, Nahyan, 2013). The placement of kalam above hadith would itself have troubled strict traditionalists.

His substantive rules for hadith evaluation press further in the same direction. He calls for assessing the content of traditions rationally, not merely auditing their chains of transmission, and specifically demands the rejection of hadith that describe God in anthropomorphic terms. This aligned him unambiguously with the mutakallimun in their ongoing rivalry with hadith-oriented scholars (Fancy, Nahyan, 2013). On the question of epistemological weight, he holds that only mutawatir reports (those transmitted by so many independent chains that collusion in error is impossible) yield certain knowledge; singular reports can rise to that level only when they are accompanied by demonstrative rational argument, a position that makes reason the arbiter of what counts as revelation’s strongest evidence (Fancy, Nahyan, 2013).

These rationalist commitments are held alongside one genuinely traditionalist commitment: Ibn al-Nafis upholds the collective moral probity of all Companions of the Prophet, rejecting the Mu’tazili position that some Companions lost that status through their conduct in the first civil war (Fancy, Nahyan, 2013). He also endorses figurative interpretation (ta’wil) of traditions that appear rationally or legally absurd, placing himself on the rationalist side of the most contentious hermeneutical debate of his era and against the traditionalist insistence on accepting the apparent sense of texts without reinterpretation (Fancy, Nahyan, 2013).

The Theological Novel: Fadil ibn Natiq

Ibn al-Nafis’s Risalat Fadil ibn Natiq (Letter of the Virtuous Rational Being) is a philosophical novel of the 1260s–1270s, and its interpretation requires understanding the precise intellectual target it opposes. Ibn al-Nafis wrote it as a direct response to Ibn Tufayl’s Hayy ibn Yaqzan, a fact his own biographers noted, though they confused Ibn Tufayl’s text with the earlier philosophical recital of the same name by Ibn Sina (Fancy, Nahyan, 2013). Ibn Tufayl’s text begins by announcing an esoteric “oriental philosophy” whose truths can be spoken publicly only in riddles, strongly implying that the exoteric religion of the masses is inferior to the mystical path available to the philosophical elite (Fancy, Nahyan, 2013). The implication becomes explicit in the climax: the philosopher Hayy concludes that the masses, including the most intelligent traditionalist scholars, are no better than irrational animals (ghayr al-natiq), capable only of the literal reading of scripture and unable to attain genuine philosophical insight (Fancy, Nahyan, 2013). Where Ibn Tufayl’s text narrates a hermit who reaches mystical union with the divine by unaided rational contemplation of nature, bypassing revealed religion entirely, Ibn al-Nafis constructs a counter-narrative designed to show that this philosophical achievement is an illusion.

The title is a polemical pun. In the climax of Ibn Tufayl’s Hayy ibn Yaqzan, the philosopher Hayy concludes that the religious masses are “no better than unreasoning animals” (ghayr al-natiq), capable only of the literal interpretation of scripture. Ibn al-Nafis responds by naming his own protagonist Fadil ibn Natiq — the virtuous (fadil) rational being (ibn natiq) — asserting that the people who adhere to scripture literally are not irrational animals but genuinely rational human beings (Fancy, Nahyan, 2013).

The philosophical argument of the novel works through deliberate narrative design. Unlike Ibn Tufayl’s Hayy, who moves systematically from natural observation to metaphysical and then spiritual knowledge, Ibn al-Nafis’s protagonist Kamil stays rigorously within empirical description and never ascends to metaphysical language; the celestial world, so prominent in Ibn Tufayl’s account, is entirely absent (Fancy, Nahyan, 2013). Ibn al-Nafis blocks the independent path to theological truth in three ways: keeping to the empirical, omitting the celestial, and restructuring the narrative so that Kamil never resolves theological questions on his own but only after encountering other human beings and coming into contact with revelation (Fancy, Nahyan, 2013). Once Kamil has encountered revelation, he uses the Avicennian argument from necessary and contingent being to prove God’s existence, and a falsafa-style argument from human sociality to establish the necessity of prophethood — demonstrating that Ibn al-Nafis was genuinely versed in the philosophical tradition he was critiquing (Fancy, Nahyan, 2013).

The crucial move comes after this. Kamil does not then reason forward from first principles to discover religious truths independently; instead, he proceeds to rationalize a posteriori the already-known contingent details of the Prophet’s genealogy and mission — an ex post facto justification of what revelation has already established, not an independent derivation of it (Fancy, Nahyan, 2013). For Ibn al-Nafis, reason has no independent path to religious truth; all subsequent theological inquiry must proceed by taking both reason and revelation into account, and the two remaining three parts of the novel’s four-part structure are concerned exclusively with matters accessible only through transmission and revelation (Fancy, Nahyan, 2013). The principle is stated explicitly: “once the necessity of revelation and the veracity of the Prophet has been established rationally, all subsequent religious inquiry … must proceed by taking into account both reason and revelation” (Fancy, Nahyan, 2013). In cases where reason reaches the limits of its metaphysical inquiry, revelation supplies the missing premise — and this solution is not suprarational but coheres with reason (Fancy, Nahyan, 2013).

The Fadil ibn Natiq attempts the philosophical reconciliation that earlier synthesizers of kalam and falsafa, including al-Razi himself, had left incomplete: it defends simultaneously the rationality of revelation and its necessity for arriving at genuine theological truths (Fancy, Nahyan, 2013). To appreciate how Ibn al-Nafis positioned himself, it is necessary to see the three-way landscape he was navigating. First, the falasifa proper: they inherited from Plotinus a conception of God as absolute unity that made positive divine descriptions logically problematic. Since any positive attribution to the One would compromise its unity, God could be described only in negative terms, a position one modern scholar characterizes as “a counsel of despair for would-be-theologians” (Fancy, Nahyan, 2013). Ibn Sina elaborated this inheritance with characteristic precision, developing the essence/existence distinction and the necessary/contingent-existent categories, and situating God at the apex of a Neoplatonic emanation scheme that produced ten intellects, the celestial spheres, and the sublunar world (Fancy, Nahyan, 2013). Second, the philosophical Sufis: Ibn Tufayl concurred with Ibn Sina that revelation cannot yield certainty on theological matters, but attempted to salvage theology by turning to mystical experience (dhawq) as a validation of the Avicennian emanation scheme, treating immediate inner experience as the substitute for the demonstrative proof that revelation allegedly cannot supply (Fancy, Nahyan, 2013). Third, the rationalist mutakallimun: a group of twelfth- and thirteenth-century Shafi’i theologians, above all Fakhr al-Din al-Razi and his students, accepted the falasifa’s demand for demonstrative proof and concluded that scripture could not serve as evidence in properly demonstrative theological arguments; if a rational demonstration contradicted revelation, they held, revelation would need to be interpreted metaphorically to conform (Fancy, Nahyan, 2013). On the far traditionalist side, Ibn Taymiyya attacked what he called “philosophical Sufis,” including Ibn ‘Arabi, al-Qunawi, and Ibn Sab’in, for upholding the doctrine of the unity of being (wahdat al-wujud) and combining Avicennian metaphysics with Sufi gnosis in a way that bypassed the authority of revelation entirely (Fancy, Nahyan, 2013).

Ibn al-Nafis differs from Ibn Sina on the function of revelation in theology: while Ibn Sina holds that revelation should stimulate philosophical inquiry at most, speaking in symbols without providing the substance, Ibn al-Nafis insists that revelation must not only stimulate but must actually provide the means for the rational elite to ascertain the true nature of the Divine (Fancy, Nahyan, 2013). He defines kalam accordingly as a science using both rational and divinely transmitted premises, making it the most noble of the religious sciences (Fancy, Nahyan, 2013).

The title Schacht and Meyerhof gave the text in their 1968 edition — Theologus Autodidactus — is therefore a misnomer that has distorted its reception. The goal of the text is not to show how a person can independently arrive at all the truths of revelation; such a goal would contradict Ibn al-Nafis’s central conviction that revelation is necessary for arriving at theological truths. The goal is to show that exoteric revelation is itself rational, and should therefore be accepted within a demonstrative argument (Fancy, Nahyan, 2013).

The Discovery of Pulmonary Circulation

The Galenic Framework and Its Problem

To understand what Ibn al-Nafis did, it is necessary to understand what he was working against. Galen’s physiology described the body as three near-separate anatomical systems centered on the liver (nutrition through veins), the heart (vitality through arteries), and the brain (sensation and movement through nerves) (Nutton, 2023). In this model, venous blood was produced by the liver, flowed outward to nourish the body, and some portion passed from the right ventricle to the left ventricle through invisible pores or perforations in the interventricular septum, where it mixed with air from the lungs to become arterial blood. Galen was aware that the pulmonary artery carried blood from the heart to the lungs, but regarded this as a secondary route (Nutton, 2023).

Arabic medical physiology reproduced this system essentially unchanged. The movement of blood in both venous and arterial systems was understood as always centrifugal — flowing outward from the liver or heart to the periphery — with no conception of return circulation (Ullmann, 1978). The three types of pneuma (natural, vital, psychic) mediated between the material body and the functional faculties, originating respectively in the liver, heart, and brain (Ullmann, 1978).

What Ibn al-Nafis Argued

Ibn al-Nafis asserted, correctly, that the blood in the right ventricle of the heart must reach the left ventricle by way of the lungs alone, and not through a passage connecting the ventricles, as Galen had maintained (Pormann, 2007). In his commentary he wrote: “The substance of the heart is solid in this region and has neither a visible passage, as was thought by some persons, nor an invisible one which could have permitted the transmission of blood, as was alleged by Galen. The pores of the heart there are closed and its substance is thick.” (Temkin, 1973)

He denied both the septum pores and, according to Saad and Said, the coronary pores that Galen had also posited, and further predicted that there must be small communications between the pulmonary artery and the pulmonary vein — a prediction that preceded Marcello Malpighi’s discovery of pulmonary capillaries by some four centuries (Saad Said, 2011).

Ullmann emphasizes that Ibn al-Nafis reached this conclusion not through systematic physiological research but through logical deduction from the known impenetrability of the septal wall — a point he regards as essential to evaluating the discovery’s significance (Ullmann, 1978). Pormann and Savage-Smith concur that this was a conceptual refinement of the anatomy and blood-flow in the heart and lungs, distinct from Harvey’s later demonstration of the continuous circular motion of blood throughout the entire body (Pormann, 2007).

Ibn al-Nafis also discredited the humoral theory of the four bodily fluids after his work on pulmonary and coronary circulation (Saad Said, 2011).

The Context of Anatomical Practice

Ibn al-Nafis’s revision of Galenic cardiac anatomy was exceptional within the Islamic medical tradition. Systematic human anatomical dissection was not practiced in medieval Islamic society — as it was not in medieval Christendom. Islamic anatomical writings remained generally conservative, deviating little from their Hellenistic models (Pormann, 2007). Abd al-Latif al-Baghdadi’s observation that the human mandible is a single bone, not two as Galen claimed — derived from examining famine skulls in Egypt — is another rare exception to this conservatism, but it too had no subsequent influence (Ullmann, 1978).

Physiology and the Soul

The most significant contribution of Fancy’s study is its demonstration that the pulmonary transit was not an isolated anatomical observation but a direct corollary of Ibn al-Nafis’s philosophical psychology — what Fancy calls his “hylomorphic psychology.” This reframes the discovery from a piece of empirical anatomy into the conclusion of a systematic metaphysical argument.

The Soul and the Whole Body

At the center of Ibn al-Nafis’s physiology is a radical claim about the soul’s relationship to the body. Repeatedly throughout his Commentary on the Canon, he asserts that the soul is related not to any specific organ or to the spirit alone, but to the entirety of the body: “the soul is related primarily neither to the spirit nor to any organ, but rather to the entire matter whose temperament is prepared to receive that soul” (Fancy, Nahyan, 2013). This position departed from all his Islamic predecessors. Avicenna had located the soul’s primary connection with the heart; Ibn Tufayl identified the soul even more tightly with the vital spirit of the heart, grounding his mystical physiology on that nexus; Qusta ibn Luqa assigned the soul to act first through the vital spirit and then through the brain. Ibn al-Nafis rejected all of them (Fancy, Nahyan, 2013).

The practical physiological consequence was a redefinition of chief organs. While Avicenna defined chief organs as the bodily locations of the primary faculties, Ibn al-Nafis defined a chief organ as “the efficient origin of the spirit that carries these faculties.” On this basis he reduced the traditional three chief organs (liver, heart, brain) to two: the heart as the organ that generates the spirit, and the brain as the organ that cools and tempers it. The liver, he states flatly, is not a chief organ at all (Fancy, Nahyan, 2013).

He also denied the existence of the vital faculty altogether — a conclusion forced by his psychology. If the soul is connected to the entire body, the body is already prepared to receive psychic faculties directly; there is no need for a mediating vital faculty to prepare organs for that reception. He states: “The truth is that this faculty does not exist, for that which prepares the body to receive the psychic faculties is the soul’s association with the body” (Fancy, Nahyan, 2013). This was a direct rejection of Avicenna’s central reinterpretation of Galenic physiology (Fancy, Nahyan, 2013).

In Ibn al-Nafis’s scheme, the spirit and the faculties stand in a reciprocal hylomorphic relationship: “the spirit is the material origin of the faculties, while the faculties are the formal origins of the spirit” (Fancy, Nahyan, 2013). The spirit is continuously generated in the heart — necessarily so, because Ibn al-Nafis recognizes that it is created very hot and fine and therefore breaks down rapidly, requiring constant regeneration (Fancy, Nahyan, 2013). The brain’s role is to receive this hot spirit from the heart and cool it; the spirit in the nerves is consequently thicker than the spirit in the arteries, because the cooler neural environment thickens it to the consistency required for transmitting the psychic faculties. On this point Ibn al-Nafis sides with physicians like Qusta ibn Luqa and against Ibn Sina, who denied that the spirit undergoes transformation in the brain (Fancy, Nahyan, 2013).

Soul, Spirit, and Bodily Resurrection

The background to Ibn al-Nafis’s solution to bodily resurrection requires understanding what his predecessors had attempted. Ibn Sina’s definition of soul as the “first perfection of a natural instrumental body” derived from a Neoplatonic reading of Aristotle that treated entelechy as a “perfection” transcending its bodily effects, enabling the soul’s separability after death (Fancy, Nahyan, 2013). But this incorporeality generated an intractable puzzle: since matter is the only individuating principle in Ibn Sina’s Aristotelian universe, he was never able to explain how separated incorporeal souls maintain their distinct individuality. He acknowledged the problem but never resolved it (Fancy, Nahyan, 2013). Ibn Tufayl proposed a different solution: he tied the soul to the spirit (ruh), treating the spirit as analogous to the fifth celestial element and therefore imperishable, which in principle guaranteed the soul’s continued individuality after death. But this committed him to a purely spiritual afterlife and undercut the Islamic doctrine of bodily resurrection (Fancy, Nahyan, 2013).

Ibn al-Nafis adopted Avicenna’s arguments for the soul’s incorporeality while rejecting both the older kalam view of a corporeal soul and the Aristotelian definition of soul as form (Fancy, Nahyan, 2013). This made the problem of individuation — how an incorporeal soul maintains its distinct identity after the death of the body — unavoidable for him.

His solution drew on hadith rather than philosophy. The ‘ajb al-dhanab, a nucleus of mixed matter generated from the seminal mixture at conception, is described as imperishable in the Muwatta’ of Malik ibn Anas. Ibn al-Nafis invokes this report as the missing premise that philosophy alone cannot supply: the soul, on becoming attached to the body at conception, becomes permanently attached to this nuclear matter; after death the soul remains with the nucleus while the rest of the body decomposes (Fancy, Nahyan, 2013). At resurrection, the soul stirs and the nucleus nourishes itself by attracting and transforming surrounding matter until the full body grows again (Fancy, Nahyan, 2013). The individuation problem is solved because the nucleus persists (Fancy, Nahyan, 2013). The philosophical problem of individuation is thereby solved by turning to revelation — “there is no way of rationally determining whether the original mixed matter actually survives throughout one’s life” (Fancy, Nahyan, 2013). This is Ibn al-Nafis’s method in concentrated form: reason is pursued to the limit of what it can establish, then revelation supplies what is left.

By attaching the soul to the ‘ajb al-dhanab rather than to the spirit of the heart, Ibn al-Nafis simultaneously severed the heart-spirit-soul nexus that underpins Ibn Tufayl’s claim that mystical states achieved through the heart could yield genuine theological knowledge independent of revelation (Fancy, Nahyan, 2013). The physiology and the theology are locked together: to undermine Ibn Tufayl’s epistemology he had to reconstruct the body’s architecture.

His new embryology carries the same logic into generation. Neither the male nor female semen possesses an active fashioning faculty; instead, when the two semens combine in the womb and produce a balanced temperament, the soul emanates natural faculties directly to this mixed matter from its Creator — bypassing the spirit-mediated mechanism that both Galen and Aristotle had posited (Fancy, Nahyan, 2013). Ibn al-Nafis embedded a concise statement of this understanding in Fadil ibn Natiq, where Kamil’s spontaneous generation is described not through a heart-spirit nexus but through a balanced temperament of the whole body from which the spirit then forms (Fancy, Nahyan, 2013).

The New Physiology as Defense of Traditionalism

Fancy’s central argument is that Ibn al-Nafis’s new physiology buttresses the same theological commitments as his Fadil ibn Natiq: by dismantling the heart-spirit-soul nexus on which Ibn Tufayl’s epistemology depended, his reconceptualized anatomy removes the physiological basis for the claim that mystical experience can yield theological truths independent of revelation (Fancy, Nahyan, 2013). The soul’s attachment to the whole body, the reduction of chief organs to heart and brain, the denial of the vital faculty, and the ‘ajb al-dhanab resurrection mechanism all hang together as a unified position with both theological and physiological consequences.

Historians of medicine have tended to treat references to spirits and faculties in Islamic medical writing as straightforward adherence to Galen, missing the substantive transformations that individual physicians introduced (Fancy, Nahyan, 2013). Ibn al-Nafis’s physiology is the most radical case: it emerges not from tinkering with Galenic parameters but from a wholesale reconstruction of the soul-body relationship in response to theological pressures that historians focused on Harvey have had little reason to examine (Fancy, Nahyan, 2013).

The Fadil ibn Natiq targets three overlapping groups simultaneously: the falasifa in the strict sense, the Avicennian mutakallimun such as Fakhr al-Din al-Razi who adopted the falasifa’s epistemological standards, and most urgently the monistic Sufis exemplified by Ibn Tufayl and Ibn ‘Arabi (Fancy, Nahyan, 2013). Ibn al-Nafis’s alignment with anti-philosophical Sufi scholars like Ibn Taymiyya and al-Dhahabi is confirmed not only by his arguments but by a specific historical parallel: both Ibn Taymiyya and Ibn al-Nafis blamed the Mongol invasions as divine punishment for sins associated with the falasifa and philosophical Sufis (Fancy, Nahyan, 2013). Ibn al-Nafis’s text specifies drunkenness and homoeroticism as the sins in question, vices the traditionalist camp consistently associated with the philosophical and Sufi milieus (Fancy, Nahyan, 2013).

His anti-Sufi stance also made him particularly valuable for the Tibb al-Nabi (Prophetic Medicine) movement. That project needed not only a physician willing to criticize Avicennian medicine as insufficiently Islamic, but one who could also rebuke the Sufis who had gone in the opposite direction: rejecting physical medicine altogether on the grounds that accepting medical treatment betrayed a lack of complete trust in God (tawakkul). Ibn al-Nafis, as a committed traditionalist and a practicing physician, was suited to make both arguments simultaneously (Fancy, Nahyan, 2013).

The hylomorphic psychology is therefore the single philosophical commitment from which both the theological argument of the Fadil ibn Natiq and the anatomical proposal of the pulmonary transit follow as consequences. The reconceptualization of the soul-spirit relationship that dismantles Ibn Tufayl’s justification for mystical epistemology is the same reconceptualization that drives Ibn al-Nafis’s rejection of Galenic cardiovascular anatomy (Fancy, Nahyan, 2013).

The Discovery of Pulmonary Circulation: A Physiological Necessity

Why the Blood Had to Pass Through the Lungs

Fancy’s reconstruction of the pulmonary transit discovery gives it an internal logic invisible in the standard account. Ibn al-Nafis’s concern was not primarily anatomical but about the conditions required for spirit generation. The heart generates the spirit by producing extremely fine blood that mixes extensively with air; for this, the blood arriving in the left ventricle must already be very fine and air-rich. Thick blood passing through a porous septum directly from the right ventricle would corrupt the spirit’s substance (Fancy, Nahyan, 2013). The anatomical proposal follows from the physiological requirement: “since one of the heart’s functions is to generate the spirit, and that can only be using very fine blood that is extensively mixed with air, it must contain very fine blood and air in order to generate the spirit from their mixture” (Fancy, Nahyan, 2013).

The mechanism he describes is precise. The artery-like vein (what we call the pulmonary artery) has two coats with very small pores; only the finest blood seeps through these pores into the lumen of the lungs, where it mixes with the large quantity of air and becomes appropriate for spirit generation in the left ventricle (Fancy, Nahyan, 2013). Thicker blood that does not pass through these pores remains in the vessel and nourishes the lung tissue (Fancy, Nahyan, 2013). The terminology reflected Galenic convention: for Ibn al-Nafis and all physicians working in the Galenic tradition, veins are vessels whose primary function is to carry blood and arteries are vessels whose primary function is to carry spirit, so the vessel emerging from the right side of the heart was naturally called the “artery-like vein” (pulmonary artery) and the vessel entering the left side from the lungs was the “vein-like artery” (pulmonary vein) (Fancy, Nahyan, 2013).

The hylomorphic psychology is therefore the motor of the anatomical discovery. As Fancy states: “The anatomical proposal is nothing more than a corollary of his new psychology and physiology” (Fancy, Nahyan, 2013).

Only the Left Ventricle Beats

Among the novel physiological consequences of Ibn al-Nafis’s denial of the vital faculty is an unprecedented claim about cardiac mechanics. In the absence of a vital faculty, heart movement requires a different motive cause; Ibn al-Nafis locates it in the faculty of locomotion acting through the spirit, making the heart’s beat an intentional motion of the soul, analogous to the voluntary movement of a limb muscle, though not consciously perceived (Fancy, Nahyan, 2013). Since he holds that heart movement is an intentional motion caused by the soul acting through the spirit, and since the spirit is generated only in the left ventricle, he concludes that only the left ventricle actively beats (Fancy, Nahyan, 2013). The right ventricle absorbs blood not by beating but through a natural absorptive faculty, like other organs (Fancy, Nahyan, 2013). In the passage in Fadil ibn Natiq where Kamil observes the heart, Ibn al-Nafis quietly encodes this understanding: “its right ventricle full of blood, its left ventricle full of spirit, and that this ventricle contracts so that the spirit penetrates by the arteries into the organs, then expands again” — earlier historians read this as Galenic orthodoxy, but Fancy shows it is in fact a condensed statement of the new understanding (Fancy, Nahyan, 2013).

A New Theory of Pulse

Ibn al-Nafis’s denial of the vital faculty also required him to reconstruct Galen’s theory of pulse. Galen had argued that arteries expand and contract through a vital faculty communicated from the heart through their tunics, drawing in cool air to ventilate the innate heat (Fancy, Nahyan, 2013). This mechanism depended on the vital faculty Ibn al-Nafis had rejected. His replacement: arterial contraction is a forced motion caused by the heart’s expansion, during which the spirit returns from the arteries to the heart; arterial expansion is then the natural return to their distended state. The sequence — contraction first, then expansion — is the reverse of what Galen and Avicenna had maintained (Fancy, Nahyan, 2013).

The function of the pulse in this new scheme is not aerial ventilation of innate heat but the maintenance of the spirit’s balanced temperament. The spirit must continuously shuttle between the very hot heart and the cooler arteries: if it remained always in the heart it would burn out, and if always in the arteries it would thicken (Fancy, Nahyan, 2013). The purpose of the pulse is “to help disperse the spirit from the heart to the rest of the body and to help ensure the proper temperament and texture of that spirit” (Fancy, Nahyan, 2013). Both the pulmonary transit and the new pulse theory serve the same requirement: the spirit must remain extremely hot, fine, and pure in order to receive the faculty of animation from the soul (Fancy, Nahyan, 2013).

The Mujaz Question

Ibn al-Nafis’s Mujiz al-Qanun (Epitome of the Canon) was the text through which he was most widely known in the pre-modern Islamic world; it was frequently copied and commented upon, and conservative hadith scholars promoted it as his key contribution to medicine (Fancy, Nahyan, 2013). Fancy’s study raises a serious challenge to its authenticity.

The problem is internal contradiction. In the Commentary on the Canon and related works, Ibn al-Nafis denies the vital faculty, reduces the chief organs to heart and brain, and grounds his whole physiology in a hylomorphic psychology that ties the soul to the entire body. The Mujaz does none of these things: it defines the three chief organs as heart, liver, and brain; it affirms the vital faculty without qualification; and it defines that faculty in terms that are “straightforwardly Avicennian,” precisely the terms Ibn al-Nafis systematically dismantles in his authenticated works (Fancy, Nahyan, 2013). The Mujaz not only fails to record disagreement with these positions; it presents Avicennian physiology as even more authoritative than Ibn Sina’s own Canon. In no other work does Ibn al-Nafis aim to conform to majority opinion.

The bibliographic evidence reinforces the suspicion. The Mujaz never refers to any of his other works, and none of his other works ever mentions the Mujaz. It is absent from the most detailed biographical entries he received (Fancy, Nahyan, 2013). Fancy does not firmly attribute the text to a forger, but concludes that the internal contradictions between it and Ibn al-Nafis’s confirmed physiology are severe enough to cast genuine doubt on his authorship.

The Mujaz’s popularity among conservative scholars is itself explicable: it presented a stripped-down, non-falsafa Avicennian medicine entirely compatible with the Prophetic Medicine project, while the philosophically dense Commentary on the Canon, with its systematic dismantling of Avicennian faculty theory, was precisely the kind of text that traditionalists wanted to keep students away from (Fancy, Nahyan, 2013).

This question has consequences for how the pulmonary transit is evaluated historically. Scholars who treat the Mujaz as authentically Ibn al-Nafis’s and work outward from it have, in Fancy’s view, systematically misread what the discovery represents. The first error is terminological: historians have consistently described his proposal as the “pulmonary circulation,” when nothing in his actual physiology involves a concept of circulation; the correct term is “pulmonary transit,” and the mislabeling has led scholars to judge his account incomplete or speculative when measured against Harvey (Fancy, Nahyan, 2013). The second error is evaluative: what look like errors from a Harveyan perspective, including only the left ventricle beating and arterial contraction preceding expansion in sequence, make coherent sense within Ibn al-Nafis’s own non-mechanical framework and the principles of natural philosophy accepted in his time (Fancy, Nahyan, 2013). The transit of blood through the lungs was not a “happy guess” arrived at by logical deduction from septal impenetrability; it was the anatomical corollary of a reconstituted physiology, which was itself the corollary of a reconstructed hylomorphic psychology (Fancy, Nahyan, 2013).

Influence and the Question of Transmission

Absence of Impact within Islamic Medicine

Ibn al-Nafis’s teaching about pulmonary circulation had practically no influence within the Islamic world (Ullmann, 1978). Pormann and Savage-Smith note explicitly that “Ibn al-Nafis’ revision received little subsequent attention in the Islamic world” (Pormann, 2007). The likely reason, as Ullmann suggests, is that Islamic medicine at this period understood its task as the explanation and interpretation of tradition rather than the elaboration of something new — the same reason that Abd al-Latif’s anatomical discovery about the mandible was ignored (Ullmann, 1978).

Rediscovery in 1924

The wider significance of Ibn al-Nafis’s work was unknown until 1924, when the Egyptian physician Muhyi al-Din al-Tatawi discovered a manuscript of his commentary on Avicenna’s anatomy in the Prussian State Library in Berlin. Al-Tatawi’s subsequent doctoral dissertation at Freiburg brought the discovery to Western scholarly attention.

The Dispute about Servetus and Harvey

[DISPUTED] Whether Ibn al-Nafis’s description of the pulmonary transit influenced Michael Servetus’s 1553 account, and whether it influenced Harvey’s demonstration of full circulation in 1628, has been a longstanding question in the field. The two leading positions point in opposite directions.

Ullmann is the cautious affirmative voice: Servetus’s description of pulmonary circulation “resembles Ibn-an-Nafīs so strongly that one can hardly reject a direct influence” (Ullmann, 1978).

Temkin, in a short note from 1940 dedicated to Max Neuburger and reprinted in The Double Face of Janus, argues the opposite — and supplies the kind of internal evidence that turns a circumstantial coincidence into a question that can be answered. The textual pathway, in the first place, was not available to Servetus: “Ibn an-Nafis’ ‘Commentary on the Anatomy in the Canon of Ibn Sīnā’ has not been translated into Latin and no intermediary source is known. It had, therefore, to be assumed that Servetus developed his theory independently from Ibn an-Nafis.” (Temkin, 1977) Temkin further identifies two specific doctrinal differences that he treats as positive evidence for independent parallel discovery rather than transmission:

The contrasting views of Ibn an-Nafis and Servetus may be stated as follows: 1. Ibn an-Nafis denies the existence of pores in the septum of the heart. Servetus is silent on this point and does not exclude the possibility of blood sweating through. 2. Ibn an-Nafis thinks that the blood filters through the wall of the pulmonary artery… Servetus believes that the blood passes from the pulmonary artery into the pulmonary vein by way of intermediate vessels. (Temkin, 1977)

On the question of how the discovery should be weighted historically, Pormann and Savage-Smith insist that even if some indirect influence reached Servetus or Colombo, Ibn al-Nafis’s pulmonary transit is “of course not equivalent” to Harvey’s continuous circulation of blood throughout the body — it is a refinement of the anatomy and blood-flow in heart and lungs, not a demonstration of systemic return circulation (Pormann, 2007). Singer’s history of anatomy describes Realdus Columbus as having demonstrated experimentally that blood passes from the lungs into the pulmonary vein, noting that Columbus was preceded in the idea of lesser circulation by Servetus, and is silent on any direct transmission from Ibn al-Nafis (Singer, 1957, ch. 4). Taken together, the available evidence — no Latin translation, no known intermediary, and two doctrinal differences — supports independent discovery as the more defensible reading. The resemblance is real; the textual descent is not.

Broader Scholarly Work

Ibn al-Nafis’s Al-Shamil intended to be a comprehensive medical encyclopedia far exceeding the scale of Avicenna’s Canon. His Mujiz (Epitome of the Canon) became a standard teaching text and was later commented upon extensively (Ullmann, 1978). He also wrote on pharmacology, philosophy, and theology. He practiced medicine within the intercommunal environment typical of medieval Islamic learned medicine, where physicians of Muslim, Christian, and Jewish background worked within the same secular Greek-derived theoretical framework (Pormann, 2007).

See Also

• Avicenna
• Galen
• History of Anatomy
• Pulmonary Circulation
• Islamic Medicine
• William Harvey
• Michael Servetus
• Ibn Tufayl

Sources

• Fancy, N.A.R. (2013). Science and Religion in Mamluk Egypt. London: Routledge. [fancy-sciencereligionmamluk-2013] — Dedicated monograph; primary authority for intellectual biography, hylomorphic psychology, Fadil ibn Natiq, and physiological context
• Pormann, P.E. & Savage-Smith, E. (2007). Medieval Islamic Medicine. Edinburgh: Edinburgh University Press. [pormann-medievalislamic-2007] — Lead authority
• Ullmann, M. (1978). Islamic Medicine. Edinburgh: Edinburgh University Press. [ullmann-islamicmedicine-1978] — Lead authority
• Saad, B. & Said, O. (2011). Greco-Arab and Islamic Herbal Medicine. Hoboken: Wiley. [saad-said-greco-arab-islamic-herbal-2011]
• Temkin, O. (1973). Galenism: Rise and Decline of a Medical Philosophy. Ithaca: Cornell. [temkin-galenism-1973]
• Nutton, V. (2023). Ancient Medicine. 3rd ed. London: Routledge. [nutton-ancient-medicine-2023]
• Singer, C. (1957). A Short History of Anatomy. New York: Dover. [singer-shorthistory-anatomy-1957]