The Book of Healing by Avicenna: An Honest Review

🕑 16 min read

What This Book Is

Abu Ali ibn Sina, known in the West as Avicenna, lived from around 980 to 1037. He was born near Bukhara in what is now Uzbekistan, was a Persian speaker writing mostly in Arabic, and spent his working life as a physician and administrator at a succession of unstable Central Asian and Persian courts.

The Kitab al-Shifa is his philosophical masterwork, composed largely in the 1020s. In scale it is one of the largest single-author philosophical works ever produced. In influence it is one of the most consequential books written between Aristotle and Descartes, and it shaped both Islamic and Latin Christian thought for five hundred years.

It is also, as an object, almost unreadable in the ordinary sense. It is an encyclopedia, written to be consulted, organised by discipline, in a technical Arabic that assumes you already know the Aristotelian corpus. Nobody reads it through.

The Title Is Not About Medicine

This deserves its own section because the confusion is so persistent.

Avicenna wrote the most influential medical textbook in history. It is called al-Qanun fi'l-Tibb, the Canon of Medicine, it runs to five books, and it was a standard text in European medical faculties into the seventeenth century. That is the medical work.

The Book of Healing is philosophy. The healing referred to is the healing of the soul from ignorance, and Avicenna says so. A reader coming to it expecting humoral theory, pharmacology or clinical observation will find logic, celestial mechanics and the theory of universals instead.

The two books have been confused since the Middle Ages, and modern booksellers have not helped. If you want Avicenna the physician, buy the Canon. If you want Avicenna the philosopher, this is the one.

The Conditions He Wrote In

The circumstances of composition matter, because they are extraordinary and because they explain the book's texture.

Avicenna was never a full-time scholar. He was a working physician and, at several points, a vizier, which in eleventh-century Persia meant running an administration in a state that might collapse or be conquered within the year. He was imprisoned at least once. He travelled, sometimes in flight. He wrote the Shifa in the middle of all this, reportedly working at night after full days of official business, and by his own account and those of his students he wrote fast and revised little.

His autobiography, continued after his death by his student al-Juzjani, describes a boy who had mastered the available curriculum by sixteen, who struggled for over a year with Aristotle's Metaphysics until a chance purchase of a commentary by al-Farabi unlocked it, and who then gave alms in gratitude.

He died at about fifty-seven, in Hamadan, of an illness he attempted to treat himself.

What Is Actually Inside

The work has four large divisions.

Logic comes first, following the expanded Aristotelian organon as it was received in Arabic, including the Categories, interpretation, syllogistic, demonstration, dialectic, sophistical refutations, rhetoric and poetics.

The natural sciences follow: physics, the heavens, generation and corruption, meteorology, minerals, plants, animals, and then the psychology, which is where the flying man appears. This last section, on the soul, is the most read part of the whole work.

The mathematical sciences cover the classical quadrivium of geometry, arithmetic, music and astronomy, and Avicenna's treatment is competent and much less original than the rest.

Metaphysics comes last and is the heart of the book. This is where the essence and existence distinction, the proof of the Necessary Existent, the emanation scheme and the account of prophecy are set out.

Avicenna also produced his own condensation of the whole thing, the Najat, meaning salvation or deliverance, and much of what circulated in later centuries came through that shorter version rather than the full text.

The Flying Man

The most famous passage in Avicenna is a few paragraphs long and sits in the psychology.

Suppose, he says, that a person were created all at once, fully formed and mature, but created in a way that eliminated every source of sensory input. Suspended in air or in a void. In complete darkness, or with the eyes veiled. The limbs held apart so that no part of the body touches any other part or anything else. No air moving against the skin. No sound.

Such a person, he argues, would have no sensation whatever, and would have no evidence of possessing a body at all, since every route by which the body announces itself has been closed.

And yet, Avicenna says, that person would affirm that they exist.

The conclusion he draws is that self-awareness is not derived from the body or from the senses, that the self is known directly and immediately without any intermediary, and that therefore the soul is a substance in its own right rather than a function of the body.

Is It the Cogito

The comparison is made constantly and it needs handling carefully in both directions.

The similarity is real. Both arguments strip away the external world and the body and find the self still there. Both take the self's awareness of itself as immediate rather than inferred.

The differences matter more. Descartes is answering a sceptical problem: he wants one thing that cannot be doubted, and the thinking self is the residue after doubt has consumed everything else. Avicenna is not worried about scepticism at all. His question is what kind of thing the soul is, and his answer is that it is a substance, not a bodily function. His conclusion is metaphysical; Descartes's is epistemological, and only later becomes metaphysical.

Whether Descartes knew the argument is a real historical question and it is not settled. Avicenna's psychology circulated in Latin as the Liber de Anima and was read across the scholastic period, so the argument was certainly available in the intellectual environment Descartes was educated in. Direct influence has not been demonstrated, and the honest statement is that a comparable argument existed in Latin Europe for four centuries before the Meditations.

Essence and Existence

If you take one idea from Avicenna, take this one, because it restructured metaphysics.

Consider what a triangle is. You can know the definition completely, work out its properties, and reason correctly about it, without knowing whether any triangle exists anywhere. The same holds for a horse, a mountain, a person. What a thing is and whether it is are separable questions.

Avicenna's move is to treat that separability as telling us something about the things themselves rather than about our knowledge of them. In every contingent being, essence and existence are genuinely distinct, and existence is something that comes to the essence from outside rather than belonging to it. A possible thing, considered in itself, is neutral with respect to existing; something has to make it exist.

The exception is the Necessary Existent, in which essence and existence are identical, which is why it does not require anything to make it exist.

This distinction became one of the central instruments of medieval philosophy. Aquinas took it, modified it and built a great deal on it, and the long scholastic argument about whether the distinction is real or only conceptual runs from Avicenna through Averroes and Aquinas to Suarez and beyond.

The Necessary Existent

Avicenna's argument for God is different from Aristotle's and better, and it is the one that reached the Latin West.

Aristotle argues from motion: things move, movers require movers, there must be an unmoved mover. Avicenna argues from existence itself. Everything we encounter is possible in itself, meaning it could as easily not have been. Whatever is possible in itself requires a cause to bring it from possibility into actuality. A chain of such causes, considered as a whole, is itself a collection of possible things and requires a cause too. Therefore there must be something that is not possible in itself but necessary in itself.

He then derives the attributes: what is necessary in itself must be one, simple, without parts, not a body, knowing, and the source from which everything else proceeds.

Notice that this argument is not about a first event in time. It is about what sustains contingent things in existence at all, at any moment, which is why it survives the collapse of the medieval cosmology entirely intact. The argument is still discussed by philosophers of religion, in a way that most medieval arguments are not, and the version that appears in Aquinas's third way is Avicenna's, adapted.

The Ten Intellects

Between God and the world Avicenna places a graded emanation, taken from the Neoplatonic tradition that had entered Arabic philosophy partly through texts misattributed to Aristotle.

From the Necessary Existent proceeds a First Intellect. That intellect, thinking its own cause and its own contingency, gives rise to a further intellect and a celestial sphere, and the process repeats down through ten intellects and the spheres associated with them.

The tenth is the Active Intellect, and it does the work. It is the giver of forms to the sublunary world, and it is what human minds contact when they actually understand something. On Avicenna's account, human intellection is not the mind generating concepts out of sense data; it is the mind being prepared by sense data to receive a form from the Active Intellect.

The astronomy underneath all this is dead. The philosophical question it was built to answer, which is how a single simple source produces a plural world without itself becoming plural, is not dead, and Avicenna's is one of the more rigorous attempts at it.

The Naturalised Prophet

The most politically dangerous part of the system is the account of prophecy, and it follows directly from the theory of intellect.

If understanding happens by contact with the Active Intellect, then differences between people are differences in the readiness of their faculties. Most people need long training and gradual preparation. Some need very little. And at the extreme, Avicenna argues, there could be a person whose intellectual and imaginative faculties are so strong that contact is immediate and comprehensive, without study.

Such a person is a prophet. The imaginative faculty then clothes what has been received in images, narratives and laws that an ordinary community can act on, which is why revelation comes in the form it does.

Read one way this is a defence of prophecy, giving it a place in a rigorous philosophical system. Read another way it makes prophecy a rare natural talent, in principle continuous with ordinary human cognition, and makes the specific content of revelation an accommodation to popular understanding. Avicenna's critics read it the second way, and they were not being unfair.

What Ghazali Did to It

Around 1095, al-Ghazali produced The Incoherence of the Philosophers, and although it is nominally about the falasifa in general, it is substantially a book about Avicenna.

Ghazali examined twenty theses and argued that the philosophers had failed to demonstrate any of them by their own standards. Three he declared to be outright unbelief: that the world is eternal, that God knows only universals and not particular things, and that there is no bodily resurrection. All three follow from the Avicennan system.

The point Ghazali was making was subtle and is often misreported. He was not saying that reason is worthless; he was a formidable logician who wrote a manual on the subject. He was saying that these particular philosophers claimed demonstrative certainty for conclusions they had not demonstrated, and that they should be held to their own standard.

Averroes replied a century later with the Incoherence of the Incoherence, and notably he defended philosophy while agreeing with a good deal of Ghazali's criticism of Avicenna specifically, whom he regarded as having corrupted Aristotle with Neoplatonic material.

What the Latins Took

From the twelfth century the Shifa was translated into Latin, principally at Toledo, and it entered the European universities in parts under separate titles: the physics as the Sufficientia, the psychology as the Liber de Anima, the metaphysics as the Liber de Philosophia Prima.

The effect was enormous and is routinely understated in general histories of philosophy. Albert the Great worked through Avicenna carefully. Aquinas took the essence and existence distinction, the contingency argument, and a great deal of the psychology, disagreeing sharply on some points and building on others. Henry of Ghent and Duns Scotus argued about the nature of the distinction for a generation. The concept of the common nature, which shaped the entire medieval debate on universals, is Avicennan.

For a period in the thirteenth century, before Averroes displaced him in some quarters, Avicenna simply was what Aristotle meant to Latin readers.

The Eastern Philosophy Question

Avicenna refers in places to an Eastern or Oriental philosophy, al-hikma al-mashriqiyya, and to a work of that name, and this has generated a long argument.

The romantic reading holds that Avicenna possessed a secret, mystical, non-Aristotelian doctrine reserved for an inner circle, and that the Shifa is the public and exoteric version. Ibn Tufail took this view explicitly, and used it as the licence for his own philosophical novel, which he presents as delivering what Avicenna had only gestured at.

Dimitri Gutas has argued at length and, in the judgement of most specialists, convincingly, that this is a misreading. On his account the Easterners material is a different presentation of the same philosophy, written in Avicenna's own voice rather than in the inherited commentary format, and the word Eastern refers to the eastern Islamic world where Avicenna worked rather than to an esoteric orientation.

The romantic version has been more attractive to readers for eight centuries. The documentary case is against it, and anyone writing about Avicenna as a secret mystic should say that the claim is contested and losing.

How to Actually Read It

You do not read this book. You use it.

Start with Michael Marmura's translation of The Metaphysics of The Healing, published by Brigham Young University Press with the Arabic on facing pages. This is the section that matters most, it is complete, and it is well annotated. It is the edition linked below.

Jon McGinnis translated The Physics of The Healing in the same series, which is the place to go if the natural philosophy interests you.

For the psychology and the flying man, the material is available through Fazlur Rahman's work on Avicenna's account of the soul, drawing on the Najat.

Above all, read Dimitri Gutas's Avicenna and the Aristotelian Tradition alongside whichever section you tackle. It is the modern study that reconstructs what Avicenna was actually doing, corrects several centuries of misreading, and will save you from the two standard errors, which are treating him as a commentator on Aristotle and treating him as a mystic in disguise.

Frequently Asked Questions