What Does It Mean for Two Things to Be One? Johannes Clauberg on Minds, Bodies, and What Connects Them

Imagine you stub your toe on a chair leg. First, there’s the shock—a jolt running through your body. Then, almost at the same time, there’s a sharp feeling of pain. And then, maybe, you decide to hop around and say some words you’re not supposed to say.

This seems perfectly ordinary. Something happens in your body, and something happens in your mind. They feel connected—almost like one event, just looked at from two sides. Most of us never think twice about it.

But if you stop and think, it’s actually deeply strange. The body is a physical thing: it has mass, location, shape. It can be measured. The mind, whatever it is, doesn’t seem to have those properties. Your anger doesn’t weigh anything. Your thoughts don’t take up space. Your memories don’t have a color. So how can something that has no physical properties affect something that does? And vice versa? How does a thought (non-physical) make your arm move (physical)? How does a stubbed toe (physical) produce a feeling of pain (non-physical)?

This is what philosophers call the mind-body problem. And a 17th-century thinker named Johannes Clauberg was one of the first people to write an entire book just about this puzzle.

Who Was Clauberg?

Johannes Clauberg was born in 1622 in what is now Germany. He grew up in a time when a huge shift was happening in how people understood the world. For centuries, most European thinkers had followed Aristotle, who thought that everything—rocks, plants, animals, humans—had some kind of “soul” or inner principle that made it what it was. A rock’s soul made it fall downward; a plant’s soul made it grow; an animal’s soul gave it movement and sensation; a human soul added reason to all of that.

But in Clauberg’s lifetime, a French philosopher named René Descartes proposed something radically different. Descartes argued that there were really only two kinds of things in the universe: minds (which think but don’t take up space) and bodies (which take up space but don’t think). Everything else—rocks, tables, trees, animals—was just complicated machinery. This was called Cartesianism (from Descartes’s Latin name, Cartesius).

Clauberg became one of Descartes’s most important followers. But he wasn’t just a copycat. He tried to solve a problem that Descartes had left unclear: if minds and bodies are completely different kinds of stuff, how can they possibly interact? How does your mind make your body do things? And how does your body make your mind feel things?

Three Answers to the Puzzle

Clauberg wrestled with this question throughout his career. Philosophers today still argue about what he really thought. But roughly, he considered three possible answers.

Answer 1: Maybe They Don’t Interact at All (Occasionalism)

One possibility is that minds and bodies never actually interact. It just looks that way.

Imagine two clocks that are perfectly synchronized. Every time one clock strikes the hour, the other strikes the hour at exactly the same moment. But the two clocks aren’t connected. They’re just set to the same time. If you saw them side by side, you’d probably think one caused the other to chime. But you’d be wrong.

Some philosophers (later called occasionalists) thought the mind and body are like those two clocks. When you stub your toe, the body event doesn’t cause the pain in your mind. Instead, God steps in at exactly that moment and produces the pain in your mind, using the body event as a “occasion” or trigger. And when you decide to move your hand, your mental decision doesn’t cause the hand to move—God steps in again and makes your hand move, using your decision as the occasion.

Clauberg sometimes sounds like he believes this. He says things like: “there cannot be found in the universe two things conjoined that are more dissimilar and more generically different than body and soul.” And he describes bodily motions as “merely procatarctic causes” that “give occasion” to the mind to produce its own ideas. This seems to say: body events don’t make the mind have experiences. They just provide the opportunity.

But here’s the thing—Clauberg never actually says that minds and bodies can’t be causes. He just says they can’t interact naturally, on their own. And he never gives the big, sweeping arguments that other occasionalists gave. So maybe that’s not his final answer.

Answer 2: They Do Interact, Just in a Weird Way (Interactionism)

Another possibility is that minds and bodies really do affect each other—but not in the normal way one billiard ball affects another. Maybe causation is broader than we usually think.

Normally, when we say “A causes B,” we mean that A does something to produce B. The cue ball hits the eight ball, and the eight ball moves. But what if causation just means “A and B are connected in a dependable way”? On this view, whenever you stub your toe, your mind reliably feels pain. And whenever you decide to raise your arm, your arm reliably rises. That dependable connection might be all causation really is.

Some scholars think Clauberg took this route. They argue that he expanded his definition of “cause” over time, so that it could include relations of dependence that don’t involve one thing actively producing another. On this reading, the mind and body are genuine causes of each other’s states—but their way of causing things is different from physical causation.

The problem with this reading is that Clauberg seems to keep a pretty strict definition of causation. He defines a cause as “a principle that gives being to another thing different from itself.” That sounds like active production, not just dependable connection.

Answer 3: They’re Connected Like a Sign Is Connected to What It Means (Semiotic Union)

This is the most interesting possibility—and the one that might be closest to what Clauberg really believed.

Think about language. The word “dog” doesn’t look like a dog, sound like a dog, or smell like a dog. There’s no natural connection between the word and the animal. But if you know English, hearing “dog” makes you think of a furry, barking creature. The word signifies the animal, even though it doesn’t cause the animal to appear.

Clauberg thought the mind-body relationship might be like that. Your bodily states are like words, and your mental experiences are like what those words mean. They’re connected, but not by causation. They’re connected because God set up a kind of language. When your toe is damaged in a certain way (a kind of “sentence” in the language of the body), your mind has the experience of pain (the “meaning” of that sentence). And when you decide to raise your arm (a kind of “sentence” in the language of the mind), your body raises its arm (the “meaning” of that sentence).

This explains why the connection feels so tight and automatic—like the word “dog” immediately makes you think of the animal. But it also explains why the connection seems arbitrary. Why does a stubbed toe produce pain and not, say, a ticklish sensation or the color blue? There’s no logical reason. It’s just how the language is set up. Clauberg says that “through his wisdom and freedom, God has willed that these acts of such different kinds be united in a human being, such that the one refers to the other, without there being any similitude between them.”

On this view, the human being isn’t a single unified thing. It’s more like a federation or a friendship—two different things that have agreed (or been designed) to work together. Clauberg even uses those exact metaphors: “federation” and “friendship.”

Why Does Any of This Matter?

You might be thinking: okay, so a dead German guy had some weird ideas about minds and bodies. Who cares?

But this puzzle is still alive today. Every time a neuroscientist tries to figure out which parts of the brain light up when you feel love or fear, they’re wrestling with the mind-body problem. How can a pattern of neurons be a feeling? How can the physical brain produce non-physical experience?

And this isn’t just an academic question. It matters for how we think about:

Artificial intelligence: If you build a machine that acts exactly like a human, does it have a mind? Or is it just a clever simulation?
Free will: If your decisions are just the result of physical processes in your brain, are you really choosing anything? Or are you just a complicated machine?
What happens after death: If the mind is just what the brain does, then when the brain stops, you stop. But if the mind is a different kind of thing, maybe it could survive?

Clauberg didn’t solve these problems. Nobody has. But he saw clearly that the way we think about minds and bodies has huge consequences. He was honest about how strange the relationship is. Maybe that’s the most important thing he did.

Appendices

Key Terms

Term	What It Does in This Debate
Mind-body problem	The puzzle of how non-physical thoughts and feelings connect to physical bodies
Occasionalism	The view that minds and bodies don’t actually interact; God causes mental events on the occasion of physical events
Interactionism	The view that minds and bodies really do cause effects in each other
Semiotic relation	A connection based on meaning, like the connection between a word and what it signifies
Cartesianism	The philosophical system of René Descartes, which divides the universe into thinking stuff (minds) and extended stuff (bodies)
Conjunction	Clauberg’s word for the mind-body relationship—not a true union, but a togetherness

Key People

Johannes Clauberg (1622–1665) : A German philosopher who was one of the first to write a systematic defense of Descartes’s ideas, and who wrote an entire book just on the mind-body problem.
René Descartes (1596–1650) : The French philosopher who kicked off the whole debate by arguing that minds and bodies are completely different kinds of substances, and then had trouble explaining how they interact.

Things to Think About

If minds and bodies are truly different kinds of things, can they really affect each other? Or does it just seem that way? What would count as evidence for either view?
Clauberg compared the mind-body relationship to language. But if you’re in terrible pain, does it feel like you’re just “reading” a sign? Or does it feel like something much more direct is happening?
Suppose Clauberg is right that the mind-body connection is arbitrary—that God (or nature) just set it up this way, and we can’t explain why a stubbed toe produces pain rather than something else. Does that mean science can never fully explain consciousness? Or could there still be a deeper pattern we haven’t discovered?
If you think your mind is separate from your body, does that change how you think about death? About taking care of your body? About what it means to be “you”?

Where This Shows Up

Near-death experiences and out-of-body experiences are often used as arguments that the mind can exist separately from the body—an idea Clauberg would have recognized.
The “hard problem of consciousness” in modern philosophy—why there is something it’s like to be a brain at all—is a direct descendant of the mind-body problem Clauberg worked on.
Debates about AI—whether a computer could ever genuinely think or feel, or whether it’s just simulating thought—echo Clauberg’s question of whether two completely different things can be connected in meaningful ways.
The way we talk about mental health—when we say depression is “chemical” or “all in your head,” we’re making assumptions about how mind and body relate.