What Is It to Be Something?

Here’s a strange thing philosophers noticed a long time ago, and still argue about.

If you look around right now, you’ll see a lot of things. There’s whatever surface you’re reading this on. There’s your own body. There might be a plant, a pet, a chair. All of these are beings—they exist. But when you ask “What is a table?” and “What is a cat?” and “What is a color?” you’re asking very different questions, even though the word “is” shows up in all of them. A cat is a living creature. Red is a color. A table is a piece of furniture. But what does the “is” actually mean in each case? Is there something that all existing things share just by being things that exist?

This is where Aristotle, a Greek philosopher who lived around 350 BCE, ran into a puzzle. He was trying to figure out what he called “being qua being”—which is a fancy way of saying “studying things in so far as they are things.” Not studying tables as tables, or cats as cats, but studying anything just because it is at all.

Why Can’t There Just Be a Science of Everything?

You might think: well, why not just create a single science of “everything that exists” and be done with it?

The problem is that “being” seems to mean too many different things. Aristotle noticed this. Consider the word “healthy.” There’s a healthy person (someone whose body works well). There’s healthy food (food that produces health). There’s a healthy complexion (a sign of health). These aren’t the same thing at all, yet they’re all connected—they all point back to that one central thing: a healthy organism. You can’t understand what “healthy food” means unless you first understand what it means for a person to be healthy.

Now think about “being.” A cat is a being. The color of the cat is a being. The shape of the cat is a being. But are these the same kind of being? A cat can exist on its own. The color of the cat cannot—it only exists in the cat. The shape of the cat cannot exist without the cat. So there seems to be a difference between things that are beings in their own right, and things that are beings only because they belong to something else.

The First Big Idea: Something Is What It Is

Aristotle called the things that can exist on their own “substances.” A tree, a horse, a human—these are substances. But the color of the horse, the height of the tree, the mood of the human—these are what he called “accidents” (which just means “things that happen to belong” to a substance, not “oops I dropped it”).

This already gives us a clue about what “being” really is. The central case—the most real kind of being—is substance. Everything else depends on substances to exist. If there were no horses, there couldn’t be horse-colors. If there were no humans, there couldn’t be human-moods. The color and the mood aren’t nothing—they’re real—but they’re not real in the same way a horse or a human is real.

But What Makes Something a Substance?

This is where things get complicated. Aristotle wasn’t satisfied just to say “a horse is a substance.” He wanted to know what it is about the horse that makes it a substance. What is it, deep down, that makes something a thing that can stand on its own?

He proposed several candidates:

Maybe it’s the matter. A horse is made of flesh and bones and blood. Maybe the horse’s substance is just the stuff it’s made of.

Maybe it’s the form. A horse is organized in a particular way. It has a shape, a structure, a way of working. Maybe the horse’s substance is that organization—the “horseness” that makes the flesh-and-bones into an actual horse.

Maybe it’s the combination of both. A horse isn’t just matter, and it isn’t just form. It’s matter that has taken on form.

Aristotle argued that matter alone can’t be the answer. If you strip away everything from a thing—its shape, its color, its size, its function—you’re left with something that isn’t really anything definite. Pure matter, he thought, is like a blank nothing. It can’t be what makes something a this particular thing.

Form, on the other hand, seems much more promising. Think about a statue. The bronze is the matter. But what makes it a statue—rather than just a lump of bronze—is its shape, its form. The form is what the sculptor puts into the bronze. And in the same way, what makes a living thing the kind of thing it is, is its form—the way its matter is organized so that it can live, grow, reproduce, and do all the things that kind of thing does.

For living things, Aristotle thought the form was the soul. Not a ghost inside the machine, but the actual organization and functionality of the living body. Your soul, in this picture, isn’t something separate from your body—it’s what your body is when it’s properly organized and alive.

The Second Big Idea: Potential and Actual

Here Aristotle introduced a distinction that changed philosophy forever. He noticed that things can be the same thing in two different ways: potentially and actually.

A piece of wood is potentially a table. Right now it’s just wood, but it has the capacity to become a table. Once someone carves it and assembles it, it becomes actually a table. The wood was always “table-shaped” in terms of possibility, but only later did it become table-shaped in reality.

Now here’s the interesting move: Aristotle thought that matter was associated with potentiality, and form was associated with actuality. The wood is potentially a table. The form of the table is what makes the wood actually a table. And the actual table—the combination of wood and form—is a substance.

But he went further. He thought that actuality was prior to potentiality. You might think the potential comes first—after all, the wood exists before the table. But Aristotle pointed out: how did that wood get there? From a tree. And how did that tree get there? From a seed. And where did the seed come from? From an actual tree. So in every case, what is actual comes before what is potential—not necessarily in time (the seed is temporally before the tree), but in explanation. You can’t understand what a seed is unless you understand what a full-grown tree is. The potential only makes sense in light of the actual.

The Third Big Idea: The Unmoved Mover

This led Aristotle to one of his strangest and most famous conclusions. If everything that exists can be analyzed in terms of potentiality and actuality, and if actuality always comes first in explanation, then at the very bottom of reality there must be something that is pure actuality—something with no potential at all. Something that just is, fully and completely, without any “not-yet” about it.

Aristotle called this the “unmoved mover.” It’s not a person like you or me. It doesn’t have a body. It doesn’t change. It doesn’t think about anything outside itself. Actually, Aristotle thought, this being just thinks about thinking itself—it’s awareness of its own awareness, endlessly. Why? Because if it thought about anything else, that would mean it was changing, or that it depended on something else for its goodness. This being is the most perfect thing there is, and it’s perfect just by being what it is.

This might sound pretty abstract. But here’s why it matters: Aristotle used this idea to unify all of reality. The unmoved mover is the ultimate explanation for why anything exists at all. Everything else that exists is somewhere on a spectrum from pure potential to pure actuality, and the unmoved mover is the end point that everything else is striving toward.

The Problem That Won’t Go Away

Here’s the thing: philosophers still argue about whether Aristotle’s picture works.

One big problem: if forms are what make things what they are, and forms are universal (the form of “human” is the same for all humans), but substances are particular (this specific human, not humanity in general), then how can a universal form be what makes a particular thing a substance? This is the tension that Aristotle never fully resolved. Some later philosophers thought he was inconsistent. Others thought they could find a way to make it all fit together.

Another problem: does the unmoved mover actually explain anything? Some philosophers think it’s a beautiful idea but doesn’t really do the work Aristotle wanted it to do. Others think it’s the necessary foundation for any complete picture of reality.

This part gets complicated, but here’s what it accomplishes: Aristotle’s metaphysics gives us a way of thinking about what it means for anything to exist at all. It says that existence isn’t just one simple thing—it’s a spectrum, with substances at the center and everything else depending on them. It says that to understand what something is, you need to understand its form—the way it’s organized and what it does. And it says that at the very top of everything, there’s something that just is, fully and completely, without any possibility of not being.

Nobody today accepts all of Aristotle’s conclusions. But the questions he asked—What is it to be a thing? What makes something what it is?—are still the questions philosophers ask when they do metaphysics. The answers have changed, but the puzzles haven’t gone away.

Key Terms

Term	What It Does in This Debate
Substance	The basic kind of being—something that can exist on its own, like a horse or a human
Accident	Something that exists only in a substance, like a color or a size
Form	The organization, structure, or “what-it-is” that makes matter into a particular kind of thing
Matter	The stuff something is made of, which is only potentially what it will become
Actuality	The state of being fully what something is—actually a table, not just potentially
Potentiality	The capacity to become something—wood is potentially a table
Unmoved Mover	A being that is pure actuality, with no potential, and that explains why everything else exists

Key People

Aristotle (384–322 BCE): A Greek philosopher who studied under Plato and tutored Alexander the Great. He wrote the Metaphysics (which literally means “after the physics”) as an attempt to figure out what being itself is.

Things to Think About

If you had to explain to someone what makes a thing “real,” what would you say? Is a dream real? Is a color real? Is a number real? What’s the difference between these kinds of reality?
Aristotle thought that the form of a living thing was its soul. Does that mean your thoughts and feelings are part of what makes you a substance? What if your body changes—are you still the same substance?
The unmoved mover doesn’t do anything except think about itself. Does that sound like a satisfying explanation for why the universe exists? Why or why not?
If “being” means different things for different kinds of things, can there really be a single science of “being”? Or are we stuck studying each kind of thing separately?

Where This Shows Up

Biology: When scientists say that “form follows function,” they’re echoing Aristotle’s idea that what something is made of matters less than how it’s organized and what it does.
Programming: The distinction between code (form) and data (matter) is a modern version of Aristotle’s hylomorphism. A program is matter (bits) structured by form (algorithms).
Everyday arguments: When people argue about whether something “really” exists—like whether a corporation or a nation is “real”—they’re wrestling with the same questions Aristotle asked about substance and accident.
Theology: Aristotle’s unmoved mover influenced how many philosophers and theologians thought about God, though they often disagreed with Aristotle’s specific description.