Al-Kindi and the Puzzle of the One

Here is a strange thing to think about: when you say something is, what are you really saying?

You might say “that tree is tall” or “this pizza is delicious” or “I am happy.” Each time, you are joining two things together—the tree and tallness, the pizza and deliciousness, you and happiness. But notice something: each of those sentences also makes a single thing out of two different things. The tree and tallness become one thing: a tall tree. The pizza and deliciousness become one thing: a delicious pizza. You and happiness become one thing: a happy you.

Now here is the puzzle. Everything we can talk about seems to be both one and many at the same time. A tree is one thing, but it has branches, leaves, roots, cells. A pizza is one thing, but it has crust, sauce, cheese. You are one person, but you have a body with many parts, and a mind with many thoughts. Nothing we experience is just pure oneness—everything is a mixture of unity and multiplicity.

But what if there were something that was only one? Not one-and-many, not one-in-a-certain-way, but pure, simple, absolute oneness? And what if that thing turned out to be the most important thing there is—maybe even God?

This is the question that drove a philosopher named al-Kindi, who lived in Baghdad about 1,200 years ago. He was one of the first people in the Islamic world to try to use Greek philosophy to understand God, the universe, and the human soul. And his answers to this puzzle about oneness ended up shaping debates that philosophers are still having today.

The Translator-Philosopher

Al-Kindi was born around 800 CE in Basra (in what is now Iraq) and educated in Baghdad, which at that time was one of the greatest cities in the world. He belonged to a noble Arab tribe, and people later called him “the philosopher of the Arabs.”

But al-Kindi did something more important than just think: he organized a team of translators. At the time, many Greek works on philosophy, science, and medicine had never been translated into Arabic. Al-Kindi oversaw a group of scholars who changed that. They translated Aristotle, Plato’s followers (the Neoplatonists), Euclid the geometer, Ptolemy the astronomer, and many others.

Al-Kindi wasn’t just a translator, though. He was also what you might call a “public relations person” for Greek philosophy. He believed that truth is truth, no matter where it comes from. In one of his books, he wrote:

“We must not be ashamed to admire the truth or to acquire it, from wherever it comes. Even if it should come from far-flung nations and foreign peoples, there is for the student of truth nothing more important than the truth.”

This was a bold thing to say in ninth-century Baghdad, where some people thought that Greek ideas were suspicious or even dangerous. Al-Kindi was arguing that Islam and Greek philosophy could work together—that you could be a good Muslim and still think like Aristotle or Plato.

The True One

Al-Kindi’s most important work is called On First Philosophy. In it, he tries to prove that there must be something that is purely, absolutely one—what he calls the “True One.” And this True One, he argues, is God.

His argument goes something like this:

Everything we experience is both one and many. A horse is one animal, but it has a head, legs, a tail, a digestive system. A species like “horse” is one kind of thing, but it includes many individual horses. A quality like “red” is one color, but it can appear in many different things. Even an individual person is one person made of many body parts.

Now, al-Kindi asks: what explains this? Why are things both one and many, instead of just one or just many?

He argues that nothing can cause its own unity. A horse doesn’t make itself be one horse. So there must be something outside of all these one-and-many things that gives them their unity. That something, he says, must be purely one—not one-and-many, but just one. It has no parts, no qualities, no relations. It is not big or small, not here or there, not even “good” or “wise” in the way we normally use those words. It is simply unity itself.

This is what al-Kindi calls the “True One.” And because everything that exists is a kind of unity—even to exist is to be one thing—this True One is also the cause of all existence. It is the source of everything.

Al-Kindi was influenced here by a group of Greek philosophers called the Neoplatonists, who had similar ideas about a “One” that is beyond all description. But he was also influenced by Muslim theologians of his day, the Mu’tazilites, who argued that God is so simple and unified that you cannot even say God has “attributes” (like “wise” or “powerful”) that are separate from God’s essence. For al-Kindi, any word you use to describe God would introduce multiplicity, because the word adds something to the thing. And the True One has nothing added.

Did the World Have a Beginning?

Today, most scientists think the universe began with the Big Bang about 13.8 billion years ago. But for most of human history, philosophers argued about whether the world had a beginning at all.

Aristotle and most Greek philosophers thought the world was eternal—it had always existed and always would. They had arguments for this. For example, they said that if the world had a beginning, there must have been time before the world existed, which seems weird. And they thought that something that comes from nothing is impossible.

But al-Kindi, as a Muslim, believed that God created the world. He wanted to use philosophy to show that the world did have a beginning. To do this, he borrowed arguments from a Christian philosopher named John Philoponus, who had lived 400 years earlier.

Al-Kindi’s main argument goes like this: The world is a body—it has size and shape. Any body is finite (not infinite) in size. You can’t have an infinitely large universe, because that would mean there’s an actual infinite thing, and Aristotle himself said that’s impossible. Now, time is something that is “predicated of” the body of the world—it’s how long the world has existed. If the world’s body is finite, then the time associated with it must also be finite. Therefore, the world cannot have existed forever.

But is this argument any good? Aristotle would say that al-Kindi is confusing different kinds of infinity. You can have a potential infinity—like how numbers can go on forever, or how you can always divide a line into smaller parts—without having an actual infinity (like an infinite number of things existing all at once). Aristotle thought the past could be potentially infinite: no matter how far back you go, you can always imagine going further. That doesn’t mean there’s an actual infinite number of past moments.

Al-Kindi’s response (again borrowed from Philoponus) is: but we are here now. If the past were truly infinite, then an infinite number of moments would have to have passed to get to today. And you can’t “traverse” an infinite—you can’t finish counting to infinity. So either the past is finite, or we could never have arrived at the present moment.

Philosophers still argue about whether this argument works. It’s one of those puzzles that seems simple on the surface but gets very complicated very quickly.

The Soul and the Intellect

Al-Kindi didn’t just think about God and the universe. He also thought about human beings—especially about the soul and how we know things.

He believed that the human soul is not physical. It doesn’t have a body, it doesn’t take up space, and it can think about things that aren’t physical (like numbers, shapes, or abstract ideas). He argued for this using Aristotle’s Categories, a book about the different kinds of things that exist. Since the soul is the “essence” of a human being, and since essences (or “species”) are not physical things, the soul must also be non-physical.

But how does the soul know things? Here al-Kindi has a very interesting theory.

He says the human intellect begins like a blank sheet of paper—it has the potential to think, but it isn’t actually thinking yet. This is the “potential intellect.” When you actually think about something—say, the concept of a triangle—your intellect becomes “actual.” You are now actually thinking about triangles.

But where did that concept of a triangle come from? Did you get it from seeing triangles in the world? Al-Kindi says no. He thinks you can’t get abstract ideas just from sense experience. Instead, there must be an outside source that gives your intellect these forms. This outside source is what he calls the “first intellect,” which is always thinking all the time. It’s like a light that shines on your mind, letting you see abstract truths.

This means that learning, for al-Kindi, is really a kind of remembering. In a lost work called On Recollection, he argues that we don’t really learn new things—we just remember what our souls knew before they entered our bodies. This is very similar to Plato’s idea that learning is recollection.

How to Be Happy

Given that al-Kindi thought the soul was separate from the body and that true knowledge comes from the intellect, it’s not surprising that his advice for living a good life was very intellectual. He wrote a book called On Dispelling Sadness, which is a guide to happiness.

His main argument is simple: sadness comes from losing things you care about. But you can avoid sadness by only caring about things that can’t be lost. Physical things—money, possessions, even your body—can always be taken away. But intellectual things—knowledge, truth, understanding—cannot be taken from you. So if you focus your desires on intellectual things, you will never be sad.

This sounds nice, but it’s hard to actually live by. Most of us do care about physical things—friends, family, our favorite toys, our homes. Al-Kindi knew this. That’s why his book is full of practical advice and stories to help people actually change how they feel.

One famous image he uses compares life to a sea voyage. Imagine you’re on a ship that stops at an island for a while. You might explore the island, pick some flowers, enjoy the scenery. But you wouldn’t build a house there, because you know the ship will leave soon. Life is like that island. We’re here for a short time, and then we move on. So don’t get too attached to the flowers.

Why Al-Kindi Matters

Al-Kindi wasn’t the most original philosopher. He borrowed heavily from Greeks, and some of his arguments are a bit shaky. He sometimes seems to have read about Aristotle’s ideas without actually reading Aristotle’s books. But he did something hugely important: he showed that you could do philosophy in Arabic, using Greek tools, to think about Islamic questions.

He set the stage for later, greater philosophers like al-Farabi and Avicenna (Ibn Sina), who would build on his work. He also helped create the technical vocabulary of Arabic philosophy—words that are still used today. And he defended the idea that truth is universal, that you can learn from people who are different from you, even if they lived hundreds of years ago in a different culture.

The puzzle he started with—how can anything be both one and many, and what does that tell us about the ultimate source of reality—is still alive. Scientists wonder about the unity of the universe. Theologians wonder about the simplicity of God. And you, if you think about it, might wonder about the same thing next time you look at a tree or eat a pizza and realize you’re trying to hold two thoughts in your head at once: “this is one thing” and “this is many things.”

Key Terms

Term	What it does in al-Kindi’s argument
True One	The cause of unity in all things; completely simple and beyond any description
Potential intellect	The human mind’s ability to think, before it actually thinks anything
Actual intellect	The human mind when it is actively thinking about something
First intellect	An always-active mind that provides abstract ideas to human intellects
Metaphorical agent	Something that both acts and is acted upon (unlike God, who is the “true agent”)
Ex nihilo	”Out of nothing”; creation that doesn’t use any pre-existing material

Key People

Al-Kindi (c. 800–870s CE): A noble Arab philosopher in Baghdad who organized the translation of Greek texts into Arabic and wrote the first major works of Arabic philosophy.
Aristotle (384–322 BCE): The most influential Greek philosopher; al-Kindi tried to use his ideas (often through later interpreters) to understand God, the soul, and the world.
John Philoponus (c. 490–570 CE): A Christian philosopher who argued against the Greek idea that the world is eternal; al-Kindi borrowed his arguments to prove the world had a beginning.
Plotinus (c. 204–270 CE): A Greek philosopher who argued that everything comes from a single, simple “One” that is beyond any description; his ideas heavily influenced al-Kindi’s theology.

Things to Think About

If the “True One” is completely simple and beyond any description, can we really say anything meaningful about it? Does “beyond description” itself count as a description? Is this a problem for al-Kindi?
Al-Kindi says that if you only care about intellectual things, you’ll never be sad. But is that true? Could you be sad about things that happen to other people, even if they don’t directly affect you? And if you do care about other people, doesn’t that mean you care about physical beings (their bodies, their feelings)?
The argument about the world’s eternity seems to depend on whether you can “traverse” an infinite past. But what if time itself began with the world? In that case, there wouldn’t be any time “before” the world for the past to be infinite in. Does that solve the puzzle, or just move the problem somewhere else?
Al-Kindi thought learning was really remembering—that we don’t get new ideas from experience. But when you learn a new skill, like riding a bike or playing a video game, it seems like you’re really learning something new, not just remembering it. Can al-Kindi explain this kind of learning?

Where This Shows Up

The debate about whether the universe had a beginning is still alive in cosmology. The Big Bang theory says it did, but some physicists still wonder whether the universe could be eternal in some sense. Al-Kindi’s arguments about infinity are still discussed by philosophers of time.
The question of whether God can be described is central to many religions. Al-Kindi’s view—that God is so simple that no words really apply—is similar to ideas found in mystical traditions (like Sufism in Islam, or apophatic theology in Christianity).
The idea that the mind is separate from the body lives on in modern philosophy of mind. Some philosophers today (called “substance dualists”) still argue that consciousness can’t be explained by physical processes alone.
The claim that truth is universal—that you can learn from any culture or time—is something scientists and historians rely on every day. Al-Kindi was an early champion of this idea in the Islamic world.