David Egan Philosophy

The Golden Age of Islam spanned about half a millennium, starting in the eighth century, when the Abbasid Caliphate established itself in Baghdad, and lasting until the thirteenth century, when Mongol armies laid waste to everything east of Hungary. It was one of history’s great periods of cultural flourishing, known for its innovations in mathematics, astronomy, medicine, chemistry, engineering, social science, jurisprudence, and, of course, philosophy. We still feel the influence of this flourishing today: words like algebra, chemistry, and algorithm have Arabic roots.

Because Arabic was the primary language of scholarship in the Islamic world, it’s natural to assume that most of the leading lights of this Golden Age were Arabs. But actually, a surprising number of them hailed from the Persianate lands of Central Asia. Al-Khwarizmi, father of algebra and namesake of the algorithm (he was known to Latin scholarship as Algorismus), hailed from Khwarazm in present-day Uzbekistan. Omar Khayyam, an innovative mathematician who’s better known in the West for his dark, romantic quatrains, or rubaiyat, came from Nishapur in what is now northeastern Iran. The polymath Al-Biruni, whose study of India marks him as the father of comparative religion and anthropology and whose calculations of the Earth’s diameter led him to hypothesize a continent on the far side of the world half a millennium before Columbus sailed there, was also from Khwarazm. His birth city is now called Berunyi and I saw his statue watching over us when, during a day trip, our vehicle stopped there for gas.

As to philosophy, the list of Central Asian philosophers reads like a who’s who of the leading lights of Islamic philosophy: Al-Farabi, Al-Ghazali, and the great Ibn Sina, better known in the West by his Latinized name of Avicenna, all came from the Persian-speaking lands of Central Asia.

Avicenna (c. 980–1037) was born not far from his mother’s hometown of Bukhara, where I’m writing this newsletter. He was a prodigy, who had memorized the entire Qur’an by the age of ten. As a teenager, he taught himself medicine, claiming that “medicine is not one of the difficult sciences.” Not difficult for him, at least—to this day, Avicenna is remembered as much as a physician as he is as a philosopher. His medical writings were taught in European universities into the seventeenth century.

Before I say more about Avicenna’s achievements in philosophy, I should provide some context. Medieval Islamic philosophy, like Christian and Jewish philosophy, was deeply indebted to the Greeks. The “House of Wisdom,” established in Baghdad in the late eighth century, served as a library, a research institute, and a translation workshop, where scholars rendered texts from Greek antiquity into Arabic. Many of these texts were lost to the Christian West and the translation project did the added service of preserving many texts that otherwise would have been lost for good.

Al-Kindi (c. 801–873), known as the father of Islamic philosophy, was a prominent figure in the translation movement. Not content to faithfully render Greek philosophy into Arabic, he saw it as his duty to improve on it where he could, correcting errors and proposing new arguments. And so a distinctive Islamic philosophy evolved, which contained a mix of commentary on Aristotle—Aristotle’s name at this time was synonymous with philosophy—and new ideas and arguments building on an Aristotelian base.

Of particular interest to philosophers in this first flourishing of Islamic philosophy was how to adapt Aristotelian philosophy to the revealed truths of Islam. A core tenet of Islam is tawhid, meaning the oneness of God. Muslim philosophers devised arguments, drawing on Aristotelian metaphysics, to prove God’s oneness. They pushed these arguments against polytheistic opponents, which, for them, included Christians—according to many Muslim thinkers, the trinity is evidence that Christians don’t take their monotheism seriously enough.

When you start devising philosophical arguments about the nature of God, you hit upon some even more abstract questions. For instance, when you say, “God is one,” what is the status of that is? What does it mean for anything to be at all?

In addressing this question, Avicenna drew a distinction between two different ways that a thing might be: essence and existence. This distinction still gets heavy use in philosophy to this day. As a shorthand, think of essence as whatness and existence as thatness. It is of the essence of triangles to be three-sided, of birds to have feathers, and of thoughts to be mental: essence establishes what kind of entity something is. The question of essence is distinct from existence. If all the birds in the world were to go extinct, there would no longer be any existing birds but we could still describe them as essentially feathered animals. We would know what kind of things birds are, even if we know that there aren’t any that exist. Likewise, I can rightly say that unicorns have horns on their head (having that horn is an essential characteristic of a unicorn) even though none have ever existed.

Avicenna deployed this distinction between essence and existence in one of the most ingenious and influential Medieval arguments for the existence of God. If we distinguish essence from existence, what is it that makes some things (like birds and people) exist while other things (like unicorns) don’t? Birds, people, and unicorns are all what Avicenna calls “possible existents”: nothing in their essence determines whether or not they exist. (Compare these possible existents to round squares, which necessarily don’t exist.)

Avicenna argues that some external cause is required to “preponderate” the existence or non-existence of possible existents. That is, if it’s possible for both birds and unicorns to exist, there must be some reason why birds exist and unicorns don’t.

So far so good: of any given bird, we can point to a mother bird and a father bird who loved each other very much to explain what preponderated that bird’s existence and we can tell similar stories about everything else that presently exists. Avicenna’s clever move comes when he invites us to consider the grouping of all the possible existents that have ever existed—all the birds, people, clouds, mountains, stars, and so on. What preponderated the existence of this collectivity?

The cause of this collection of possible existents can’t itself be a possible existent, since, if it were, it would just be one more part of the collection whose existence still needs to be explained. The answer, then, must be what Avicenna calls a “necessary existent.” This necessary existent is commonly known by a less technical name: God.

What’s more, and very important to a Muslim philosopher like Avicenna, there can be only one necessary existent. If there were more than one necessary existent, they would have to be different somehow. That difference would have to be explained by some further, external cause. But a necessary existent can’t be caused to be one way or another due to an external force—that would make its existence dependent on something else, undermining its necessity. So the necessary existent must be unique.

Avicenna’s originality in argument marked him out from his contemporaries. Perhaps his most strikingly original argument is his “floating man” thought experiment. Avicenna invites us to imagine a man spontaneously created out of nothing and floating in mid-air. His eyes are veiled and his limbs are splayed as he floats in a soundless space, totally deprived of any sensation. Would this person be aware of anything at all? He would lack any sensory awareness, Avicenna argues, but he would still be self-aware. He would, in short, be aware of his own essence even if he wasn’t aware of any existents.

Avicenna uses this thought-experiment to argue for a background self-awareness that underlies all our ordinary perceptions, but which we normally fail to notice. What’s more, since this self-awareness can be distinguished from any bodily awareness, Avicenna argues that we are essentially thinking beings and only contingently bodily beings. This dualistic argument trickled down to Descartes in the seventeenth century. And the idea of a necessary background self-awareness would later surface in the critical philosophy of Kant, and from there exert a powerful influence on much of the philosophy of the last two centuries.

While pre-Avicennan philosophy was largely commentary on Aristotle, post-Avicennan philosophy often took Avicenna himself to be the central figure of philosophy with whom one had to engage, either in agreement or disagreement. This applies well beyond the world of Islam, where he came to be known as “The Preeminent Master.” Thomas Aquinas and Duns Scotus in the Christian tradition and Maimonides in the Jewish tradition were deeply indebted to Avicenna, marking Avicenna out as the only Medieval philosopher to exercise a powerful influence on philosophy in all three of the Abrahamic religions.

Central Asia has not forgotten one of its greatest sons. Postage stamps in Iran and currency in Tajikistan bear Avicenna’s likeness and, in Uzbekistan, I’ve seen his portrait in museums and his name on hospitals. On a map, Bukhara looks like it’s a very long way from everything else. But in the history of philosophy, it holds a central place. 

1. The reason it’s spelled “colonel” but pronounced “kernel” is that the spelling comes from the Italian but the pronunciation comes from the French. The English word derives originally from the French “coronel,” meaning the head of a regiment. But the English spelling shifted in the 16th century to match the Italian “colonnella” (which meant the same thing), even as the pronunciation remained unchanged. (source)
2. Last month I wrote about celluloid being used as an ivory substitute in making billiard balls, and how this was the first major commercial application of a synthetic plastic. What I didn’t know until Noah Feinstein pointed it out to me is that celluloid has combustive properties that occasionally made colliding balls explode. (source)
3. The North Atlantic contains an estimated 27 million tonnes of nanoplastics, which is greater than the collective mass of all wild land mammals. (source)
4. You have millions of cells inside of you that are your mother’s, or even those of an older sibling or other relatives on your mother’s side. In a phenomenon known as microchimerism, cells pass between mother and fetus so that each ends up with cellular material from the other. (source)
5. When Turkey’s current governing party, the Justice and Development Party (AKP), first came to power in 2002, Turkey’s prisons held about 60,000 people. Today, that number is 350,000—more than the prisons in all the other 45 member states of the Council of Europe put together. (source)
6. Mobile money accounts are a system for sending and receiving money over the phone without setting up a formal bank account. The use of such accounts has grown enormously—especially in sub-Saharan Africa—from 13 million mobile accounts in 2010 to 640 million in 2023. That’s more than twice the number of Netflix subscriptions worldwide. (source)
7. During the sixteen years that George W. Bush and Barack Obama were president, their administrations filed eight emergency applications to the US Supreme Court. İn the first twenty weeks of the second Trump presidency, his administration has filed eighteen. (source)
8. For roughly four centuries, between the mid-sixteenth and mid-nineteenth centuries, the Russian Empire grew by an average of 55 square miles a day, or 20,000 square miles per year. (source)