What Makes Something Happen? Al-Ghazālī and the Puzzle of Cause and Effect

Imagine you’re sitting in your room and you see a glass of water on your desk. You reach out, push it, and it falls off the edge, shatters on the floor, and water spills everywhere. You’d probably say: I caused the glass to fall. But did you really? And what does “causing” something even mean?

Now imagine a harder question. Suppose you have a candle and you touch a match to its wick. The wick catches fire. We all know that happens. But why does it happen? What’s the actual connection between the flame and the wax? Is it possible that the match and the flame just happen to show up at the same time, every time, without one actually making the other happen?

About a thousand years ago, a Persian scholar named al-Ghazālī (al-GHAZ-ah-lee) asked himself these questions. He wasn’t just curious about matches and candles. He was worried about something bigger: if everything in the world is connected by cause and effect, where does God fit in? And if God is the one who makes everything happen, what does that mean for your choices? For miracles? For whether you can be held responsible for pushing that glass off the desk?

His answers set off a debate that’s still alive today.

The Philosopher and the Theologian

Al-Ghazālī was born around 1055 in what is now northeastern Iran. He became one of the most important intellectuals in the Islamic world. He taught at the most prestigious school in Baghdad, the Nizāmiyya Madrasa. He was a confidant of sultans and caliphs. And then, in 1095, he suddenly gave it all up. He left Baghdad, went to Damascus and Jerusalem, and made a vow never again to serve the political authorities or teach at state-sponsored schools.

Why? Because he had come to believe that working for rich and powerful people — benefiting from their money — made you complicit in their corruption. He thought his own salvation might be at risk. So he walked away.

During this period of his life, al-Ghazālī wrote his most famous work, a book called The Incoherence of the Philosophers. The title gives you a hint of what’s inside. Al-Ghazālī was taking aim at a group of thinkers known as the falāsifa (from the Greek word philosophia). These were Muslim philosophers who had inherited the tradition of Aristotle and Plato, especially through the works of a thinker named Avicenna (Ibn Sīnā), who died about twenty years before al-Ghazālī was born.

The falāsifa believed that human reason — careful logic and argument — could prove truths about the world, about God, about the soul, and about the afterlife. They thought that philosophy could arrive at the same truths that religion taught, just using a different method. Some of them even thought that reason was superior to revelation: that if a philosopher proved something with a “demonstrative proof” (an airtight logical argument), then scripture should be interpreted to fit that proof, not the other way around.

Al-Ghazālī thought this was backwards. He wasn’t against reason entirely. In fact, he used a lot of the philosophers’ own tools. But he wanted to show that the falāsifa were not nearly as logical as they thought they were. Their “proofs” weren’t airtight. They were often just repeating things they’d been taught, without examining them. And on three specific issues, al-Ghazālī said the philosophers had crossed a line: they had taught things that directly contradicted Islam.

Those three issues were:

The world has no beginning. The falāsifa (following Aristotle and Avicenna) said the universe has always existed. It wasn’t created at some point in time. It’s eternal. Al-Ghazālī said this contradicted the Qur’an, which teaches that God created the world.
God only knows general things, not details. Avicenna argued that God knows universals — categories like “humanity” or “justice” — but not individual things like “this specific person, Zayd, who is lying right now.” Al-Ghazālī said this was impossible: God knows everything, down to the smallest particular.
There is no bodily resurrection after death. The philosophers believed that after death, only the soul survives. The body decays and that’s it. Al-Ghazālī insisted that the Qur’an teaches a real, physical resurrection — bodies coming back to life.

Al-Ghazālī said that anyone who publicly taught these three positions was an apostate from Islam — and could be killed. This was a powerful (and dangerous) statement.

But here’s the strange thing: even though al-Ghazālī condemned these three ideas, he adopted many other teachings from the philosophers. Especially from Avicenna. He used their psychology. He used their ethics. And when it came to the question of causality — what makes one thing cause another — he borrowed heavily from them while also pushing back.

The Puzzle of Causality

Let’s go back to the candle and the match. Here’s what Avicenna would say: fire has a “nature” that makes it burn things. When fire touches cotton (or a candle wick), it necessarily causes combustion. This is not an accident. It’s how the universe works. The connection between fire and combustion is a necessary one, built into the fabric of reality. Given the fire and the cotton, combustion must happen.

Al-Ghazālī disagreed. Here’s the core of his argument:

The connection between what is habitually believed to be a cause and what is habitually believed to be an effect is not necessary… Their connection is due to the prior decision of God, who creates them side by side.

Let’s unpack that. Al-Ghazālī says that when you see fire touch cotton and the cotton burns, you don’t actually see a necessary connection. You see two events happening one after the other. First, the fire touches the cotton. Then, the cotton burns. But you never observe the “making” part — the invisible force that turns the first event into the second. You just see the sequence.

So how do you know the fire causes the burning? Maybe God just creates the burning at the same time as the fire touches the cotton, without the fire having any real power. The fire is just a sign, a signal. It’s like a clock: when the hour hand reaches 12, the clock chimes, but the hand doesn’t cause the chime. Both are connected by the design of the clockmaker.

This is called occasionalism. The idea is that God is the only real cause. What we call “causes” are just occasions when God creates a certain effect. Fire doesn’t burn cotton. God burns it, every single time fire touches cotton, following a pattern that God has chosen. This pattern is God’s “habit” or “custom” (sunna). It’s reliable — you can count on fire to burn things — but it’s not necessary. God could change it at any moment. If God wanted to, He could make fire touch cotton and the cotton freeze solid. That would be a miracle.

Now, you might be thinking: But that’s crazy. Fire really does burn things. We know that. We’ve tested it millions of times.

Al-Ghazālī’s response: You’ve tested the sequence. You haven’t tested the necessity. You can’t see necessity. You can only see one thing following another. And there’s a difference between “this always happens” and “this must happen.” The philosophers confused the two.

Two Different Worlds

Here’s where it gets technical, but stick with me because this is the heart of the whole debate.

Avicenna and al-Ghazālī had different ideas about what “necessity” even means. For Avicenna, something was necessary if it always happened. Fire always burns cotton? Then it necessarily burns cotton. The fact that it has never failed to burn cotton, and never will, means the connection is necessary.

For al-Ghazālī, that’s not enough. Something can always happen and still not be necessary. The key question is: Could it be different? Even if fire has never failed to burn cotton, can you imagine a world where it doesn’t? If you can — and most people can — then the connection is not necessary. It’s just actual. God chose this world, with these rules, but He could have chosen a different one.

This is a huge philosophical difference. Avicenna thinks the world flows necessarily from God’s nature. God doesn’t choose to create this world; His nature requires it. It’s like how a triangle necessarily has three sides — you can’t have a triangle without three sides, and you can’t have God without this universe.

Al-Ghazālī thinks this is wrong. God has a genuine free will. He chose this world among alternatives. The universe is contingent — it could have been otherwise. And that means the causal connections in it are contingent too. They depend on God’s free choice, not on necessity.

But Here’s the Twist

Remember how I said al-Ghazālī borrowed a lot from Avicenna? Well, even though he rejected the necessity of causal connections, he didn’t reject the idea that there might be real chains of causes in the world. In fact, he seems to have held two different possible explanations side by side, and he never definitively chose between them.

Option 1: Occasionalism. God creates every event directly, without using any intermediaries. When fire touches cotton, God creates the burning. When you decide to push the glass, God creates that decision and the movement of your hand. There are no secondary causes — no real powers in the world besides God.

Option 2: Secondary causality. God creates a chain of causes. He makes the fire, and then He gives the fire a real power to burn things. The fire actually does cause the burning, but only because God designed it that way and sustains it. The fire is a “secondary cause” — it really does something, but only because the “primary cause” (God) keeps it going.

Al-Ghazālī says explicitly, in one of his key passages: “Both these two views are possible for us.” He never settles it. Why not? Because he thinks we can’t know for sure. Observation can’t tell us whether there’s a real causal connection or just a regular sequence. Revelation doesn’t settle it either. So the smart thing to do is to suspend judgment.

This is frustrating if you want a clear answer. But it’s also honest. Al-Ghazālī is saying: this is genuinely hard. We don’t have enough information. Not every question has a settled answer.

What’s at Stake?

You might be wondering: Why does any of this matter? Who cares whether fire really burns things or God just makes it look that way?

Here’s the thing: the way you think about causality changes how you think about a lot of other things.

Miracles. If the world runs on necessary cause-and-effect, then miracles are impossible — they’d violate the laws of nature. But if the world runs on God’s free choice, then miracles are just God doing something different from His usual pattern. They’re not violations of anything; they’re just unusual acts of the same Creator.

Human freedom. If God creates every event directly, then what about your choices? When you decide to push the glass, is that really your decision, or is God creating that decision in you? Al-Ghazālī was a determinist: he thought God determines everything, including human actions. But he also thought that, for practical purposes, we should act as if we have free will. We experience ourselves making choices, and that experience is real enough.

Science. If there are no real causal connections, then science is just describing patterns — “this usually happens after that.” It can’t discover real powers or necessary laws. Some modern philosophers have argued that this is actually a pretty good description of what science does: it finds regularities, not necessities.

Responsibility. If you don’t really cause anything, can you be blamed for pushing the glass? Al-Ghazālī thought yes, because God still holds people accountable for their actions. But this is a hard question: if everything is determined by God, how can anyone be truly responsible?

The Debate Continues

Al-Ghazālī’s Incoherence of the Philosophers provoked a response from the most important falāsifa of the next generation: Averroes (Ibn Rushd), who lived in Spain. Averroes wrote a book called The Incoherence of the Incoherence, where he defended philosophy against al-Ghazālī’s attacks. He argued that Aristotle had proven the eternity of the world, and that al-Ghazālī’s arguments against necessity didn’t work.

This debate — between occasionalists and believers in secondary causes, between those who see God as the only real agent and those who think God works through natural powers — continued for centuries in Islamic theology, Jewish philosophy, and eventually Christian Europe. When al-Ghazālī’s Doctrines of the Philosophers was translated into Latin in the 12th century, many European readers thought he was a follower of Avicenna, not a critic. His work became a major source for thinkers like Thomas Aquinas.

The questions al-Ghazālī raised are still alive. Do we really observe causation, or just correlation? Is the universe necessary or contingent? What does it mean to say that something must happen? These aren’t just theological puzzles. They’re questions about the fundamental structure of reality.

Al-Ghazālī’s final position — that he couldn’t decide between occasionalism and secondary causality — might look like a cop-out. But maybe it’s actually the right attitude. Some questions, he thought, we simply can’t settle with certainty. And part of being a thoughtful person is knowing when to say: I don’t know, and here’s why.

Key Terms

Term	What it does in the debate
Occasionalism	The view that God is the only real cause; what we call “causes” are just occasions when God directly creates an effect
Secondary causality	The view that God creates chains of causes, giving created things real power to produce effects, while still being the ultimate source
Necessity	The idea that a connection between two things cannot be otherwise; al-Ghazālī argued that causal connections are not necessary, just habitual
Contingency	The idea that something could be otherwise; al-Ghazālī said the world is contingent because God freely chose it among alternatives
Demonstration (burhān)	An airtight logical proof that produces certainty; al-Ghazālī said the philosophers claimed to have these but didn’t actually
Habit/Custom (sunna)	God’s regular pattern of creating the same effects after the same causes; reliable but not necessary

Key People

Al-Ghazālī (c. 1055–1111) — A Persian theologian and jurist who left a prestigious career to become a Sufi ascetic; he wrote The Incoherence of the Philosophers to challenge the claim that philosophy could prove its conclusions with certainty
Avicenna (Ibn Sīnā, c. 980–1037) — The most important philosopher in the Islamic tradition before al-Ghazālī; he developed a complete philosophical system that explained God, the soul, and prophecy using Aristotelian logic
Averroes (Ibn Rushd, 1126–1198) — A Spanish Muslim philosopher who wrote The Incoherence of the Incoherence to defend philosophy against al-Ghazālī’s attacks

Things to Think About

Al-Ghazālī says you can’t observe a necessary connection between cause and effect — you only see one thing following another. Do you think this is right? Can you think of a case where you do seem to observe causation directly, not just a sequence?
If God (or nature, or the universe) always follows the same pattern — fire always burns cotton — what’s the practical difference between saying the connection is necessary versus saying it’s just habitual? Does it matter for how you live your life?
Al-Ghazālī held two possible explanations side by side and never chose between them. Is it okay to say “I don’t know” about a big question like this? Or should you push harder for an answer?
If everything is determined by God (or by physics), can people still be responsible for what they do? Is it fair to punish someone for an action they couldn’t have avoided?

Where This Shows Up

Science and statistics. When scientists say “correlation doesn’t imply causation,” they’re making a point very similar to al-Ghazālī’s: observing that two things happen together doesn’t prove that one causes the other.
Debates about free will. The question of whether our choices are genuinely free or determined by prior causes is still a major topic in philosophy and neuroscience.
Miracles and the laws of nature. When people argue about whether miracles are possible, they’re often repeating versions of the al-Ghazālī vs. Avicenna debate: are the laws of nature necessary or just God’s usual pattern?
David Hume (18th century). The Scottish philosopher Hume argued, like al-Ghazālī, that we never observe necessary connections between causes and effects — we only see constant conjunctions. Hume didn’t bring God into it, but his argument is remarkably similar.