Avicenna

The teaching

Taught from his own books, above all the Book of Healing, the Canon and the Remarks and Admonitions.

The floating man

Avicenna asks his reader to imagine a man created all at once and fully formed, but with his sight veiled so that he sees nothing outside, floating in empty air so that nothing touches him, his limbs held apart so that they do not touch each other. Such a man would know nothing of his body, his limbs, his heart or his brain, and yet he would not doubt for a moment that he exists. What he affirms is himself, and it is no part of his body; so the self, the soul, is other than the body, and knows itself directly.

Necessary and possible

Whatever exists is either necessary in itself or possible in itself. What is possible in itself may be or not be, and so needs a cause to be; and a chain of such causes, however long, is still a chain of possible things and needs a cause outside it. So there is a Being necessary in itself, without cause, one and simple, whose essence is nothing but its existence. In everything else essence and existence differ: horseness, taken in itself, is only horseness, neither one nor many, neither existing nor not, and receives its being from beyond itself.

From the One, the ten minds

From the Necessary, which is one, only one thing can come directly: the first intellect. Thinking of the Necessary, it gives rise to a second intellect; thinking of itself as necessary through another, to the soul of the outermost heaven; and thinking of itself as only possible in itself, to that heaven's body. So the procession runs down through the heavens to a tenth intellect, the Active Intellect, the giver of forms, which governs the world below the moon. The order of the ten is taught more fully on the page of daimons and intelligences, in the spirit realm.

The inner senses

Within, the soul has five senses as the body has five. The common sense gathers what the outer senses bring into one picture. The imagination keeps the images when the things are gone. The compositive power joins and divides them, and in human beings, when reason uses it, it becomes the power of thinking things through. Estimation grasps meanings that no outer sense can see, as the sheep perceives that the wolf is to be fled from and its own lamb to be loved. Memory keeps the meanings that estimation has grasped. Each has its seat in a chamber of the brain, from front to back.

How the mind comes to know

The human intellect begins as pure potency, like a blank tablet; with the first truths it becomes intellect in habit, then in act when it thinks, and at its height it is acquired intellect, holding the forms of things as its own. But no mind gives itself what it learns. The Active Intellect gives the forms when the soul is ready, as the sun gives light to the eye and makes colours seen; study and reflection are the readying, and understanding is the soul joined to that light.

Minds differ in how readily they are joined. Some find the middle term of a proof quickly, by intuition, without being taught; others slowly; and at the summit is a soul so pure and so strong that it grasps almost everything at once, as if lit from within. That, Avicenna teaches, is the holy intellect of the prophets, the highest of human powers.

The medicine of the Canon

The Canon teaches medicine as an ordered science. Health is the right balance of the body's temperaments and of its four humours, blood, phlegm, yellow bile and black bile, and illness is their loss of measure; the physician must know the causes, material, efficient, formal and final, to restore it. The body is kept or lost by six necessary things: the air one breathes, food and drink, movement and rest, sleep and waking, what is taken in and what is let out, and the movements of the soul, joy, anger, fear and grief among them.

He gives rules for testing a remedy too: try it as a simple substance, free of any added quality; on a simple illness, not a mixed one; on two opposite conditions, to see what it does to each; with its strength matched to the illness; watching how soon it acts and whether it acts every time; and on the human body, since a drug may act otherwise on an animal. The house teaches the Canon as the history of medicine; none of it is a guide to treatment today, and anything that troubles the body belongs with a doctor.

Why metals cannot be changed

In the Book of Healing he reasons with the alchemists. They can whiten copper until it looks like silver and colour it until it looks like gold, and they can purge it of much of its dross; but colour and cleansing are accidents laid on the surface. Each metal is a kind with its own specific form, and the difference that makes it that kind is not known to us. What is not known cannot be taken away or produced, so the art can imitate a metal, often very well, but cannot turn one metal into another.

The stations of the knowers

The last chapters of the Remarks and Admonitions describe three who turn from the world. The ascetic turns away from its goods; the worshipper keeps the prayers and the fasts; the knower turns his whole mind to the holiness of the Truth, so that its light may shine on his inmost self. The ascetic and the worshipper may still be bargaining, giving up this world for the next; the knower wants the Truth for its own sake and nothing else.

His way has stages. It begins with will, the longing to hold fast to the Truth; then comes discipline, which has three aims: to set aside all that is not the Truth, to make the commanding soul obey the soul at peace, and to make the inner self fine and gentle. Then come moments when the light of the Truth flashes on him like lightning and is gone; they come more often, until they stay, and at last he passes from himself and sees only the Truth. The knower is cheerful and smiling, humble towards the lowly as towards the great, slow to anger even when he sees wrong, generous and brave, for he no longer fears death or loss.

The dove that came down

His allegories tell the same journey in pictures, and the poem of the soul given in his name tells it most briefly. The soul came down to the body from the highest place like a dove, rare and proud, unwilling at first; it grew used to its desert home, forgot the place it came from and wept when it remembered; and now it longs to fly back, singing of the heights it knows again. His tales of the bird and of Hayy, son of Yaqzan, give the same flight its longer story.