What Does It Mean for Something to Be Real? Byzantine Philosophers and the Problem of Universals

Imagine you and your friend are looking at two different dogs—a golden retriever and a tiny chihuahua. You both agree they’re both dogs. But what does that mean? Is there something called “dog-ness” that exists somewhere, somehow, that both of these animals share? Or is “dog” just a word we made up to group together things that look similar?

This might sound like a silly question—like something a little kid would ask to annoy their parents. But it’s actually one of the most stubborn puzzles in all of philosophy. Philosophers call it the problem of universals. A “universal” is anything that can be true of many different things at once: dog, red, triangle, justice, beauty. The puzzle is: do universals actually exist somewhere? Or are they just names we use to keep things organized?

Now here’s the strange thing. For about a thousand years, the best thinkers in the Byzantine Empire—the Greek-speaking Christian empire that lasted from around 330 to 1453 CE—argued about this question. They lived in Constantinople, a city of immense wealth and learning, surrounded by ancient Greek texts that had been preserved and studied continuously. They didn’t need to rediscover Plato and Aristotle the way Western Europeans did; they’d never lost them. And they had a problem: how do you make sense of ancient Greek philosophy when you’re also a faithful Christian?

The Three Kinds of “Dog”

By the time Byzantine philosophers got seriously into this debate, they had a neat way of organizing the possible answers. They said there are three ways a universal like “dog” could exist:

Before the many (pro tōn pollōn): The universal exists in some perfect, eternal realm—like Plato’s idea of “Dog” in heaven, which all actual dogs imperfectly copy.
In the many (en tois pollois): The universal exists inside each individual thing. Your golden retriever has its own “dogginess,” and the chihuahua has its own different “dogginess,” but they’re both real.
After the many (epi tois pollois): The universal exists only in our minds, as a concept we build by noticing similarities between individual dogs.

Most Byzantine philosophers said all three are true in different ways. The universal exists “before” as God’s idea of a dog, which God used when creating dogs. It exists “in” each dog as that particular dog’s nature. And it exists “after” as the concept in your mind when you think “dog.”

This sounds like a peaceful compromise. But it hides a dangerous question.

A Philosopher on Trial

On the first Sunday of Lent every year, in Greek Orthodox churches, a long list of condemned heretics is read aloud. One name on that list is John Italos. He was a philosopher who lived in Constantinople around 1000 years ago, and the Church formally cursed him in 1082. What did he do wrong?

Italos was one of the most brilliant logic teachers of his time. He succeeded his teacher Michael Psellos (who was admired and protected by powerful friends) as the head of the Imperial School of Philosophy. Psellos had managed to study Plato and the Neoplatonists without getting into serious trouble. Italos was less careful.

What got Italos condemned was his belief that philosophy—especially logic and rational argument—could be used to examine anything, including theology. He thought that if a claim couldn’t survive logical scrutiny, it shouldn’t be believed. The Church saw this as arrogance: you can’t put God in a syllogism and test him like a science experiment.

But here’s the philosophical twist. Italos also had very specific views about universals, and those views got tangled up in his trial.

What Kind of Real Are Universals?

Remember the three types of universals? Italos had a distinctive way of thinking about the “in the many” and “after the many” ones.

He thought that when you look at Socrates, there’s something in Socrates that makes him Socrates—his particular “Socrateness.” That’s a universal “in” him. But it’s not the same universal that’s in Plato. Socrates has his own dogginess, his own humanness. Each individual has its own particular form.

Then, when your mind looks at Socrates and Plato and notices they’re both human, your mind creates a concept—“human”—that exists “after” them. That concept is abstracted from the individuals. It’s a thought in your mind.

Here’s the crucial part: Italos insisted that both of these—the universal in the individual and the universal in the mind—are real. They’re not just sounds or fictions. They’re not as fully real as God or as physical bodies, but they’re not nothing either.

He made a distinction between:

Subsistences (hupostaseis): things that exist on their own, like physical bodies and God.
Things that subsist in something else (enupostata): things that are real but need something else to exist in, like the color of an apple or the concept of dog in your mind.

According to Italos, universals “in” and “after” the many are real in the second sense. They’re not just made-up. But they’re not independently existing things either.

This might sound like a minor technical point, but it was explosive. Why? Because if you say universals exist only in our minds, you might be accused of denying that God’s ideas are real. If you say they exist independently like Plato’s Forms, you might be accused of saying there are eternal realities other than God. Italos was trying to find a middle path, but the Church saw his rationalist approach as threatening.

Why Did This Matter So Much?

You might wonder: why did anyone care this much about whether “dog” is real? The Byzantine Empire was constantly dealing with political crises, wars, theological disputes, and the looming threat of invasion. Why did philosophers spend so much time on universals?

Part of the answer is that Byzantine education was built around logic. The standard curriculum started with Aristotle’s logical works, and students spent years learning how to categorize things, make arguments, and identify fallacies. The problem of universals was a natural puzzle that arose from this training.

But there’s a deeper reason too. The problem of universals connects to questions about God, creation, and human knowledge. If universals exist in God’s mind, then studying them is a way of understanding God’s plan for the world. If they exist only in our minds, then human knowledge might be more fragile and less connected to ultimate reality. Getting universals wrong could lead to wrong ideas about God, the soul, and salvation. That’s why people were willing to put philosophers on trial over it.

Did They Solve It?

No. Philosophers still argue about universals today. The three-way framework that Byzantine philosophers used is still taught. And the basic puzzle—do categories exist in reality, in our minds, or both?—remains unresolved.

What the Byzantines did was keep the question alive through centuries when it might have been forgotten. They preserved and commented on Aristotle’s logical works, and they developed sophisticated arguments about the reality of universals that later thinkers, both in the Renaissance and in modern philosophy, would draw on.

The last great Byzantine philosopher, George Gemistos Plethon, who lived through the final decades before Constantinople fell to the Ottoman Turks in 1453, went even further. He argued that Plato was right and Aristotle was wrong, and he proposed replacing Christianity with a revived form of ancient Greek polytheism—a system where the Platonic Forms (universals) were the highest realities. His books were burned by the patriarch of Constantinople after the city fell.

So the problem of universals had real stakes. People were willing to be cursed, exiled, or have their writings destroyed over it. That’s how important it seemed—and still seems—to get straight on whether “dogness” is something real, or just a useful word.

Appendix

Key Terms

Term	What It Does in This Debate
Universal	A quality or category that can apply to many individual things (like “dog,” “red,” “justice”)
Particular	A specific individual thing (like this golden retriever, this specific apple)
“Before the many”	Universals as eternal ideas existing before any individuals, often identified with God’s thoughts
”In the many”	Universals as they exist inside each individual thing, giving it its nature
”After the many”	Universals as concepts our minds create by noticing similarities between individuals
Subsistence	Something that exists on its own, independently
Abstraction	The mental process of extracting shared features from individual cases to form a concept
Moderate realism	The view that universals are real but depend on individuals for their existence

Key People

John Italos (c. 1025–after 1082): A brilliant logic teacher in Constantinople who was put on trial and condemned by the Church for using philosophical reasoning on theological questions. He developed a detailed theory of universals as real but dependent on individuals.
Michael Psellos (1018–1078): Italos’s teacher and predecessor as head of the Imperial School. A hugely learned scholar who loved Plato and the Neoplatonists but managed to avoid condemnation.
George Gemistos Plethon (c. 1360–1452): The last major Byzantine philosopher, who rejected Christianity for a revived Platonic religion. His books were destroyed after the fall of Constantinople.

Things to Think About

If universals exist only in our minds, does that mean there’s no real difference between calling something a “dog” and calling it a “chair”? How would you decide which categories are real and which are just convenient?
Italos insisted that universals are real but depend on individuals to exist. Does this position actually avoid the problems of both saying they’re totally unreal and saying they’re independent realities? Or does it just push the difficulty somewhere else?
Why do you think the Church saw Italos’s rationalist approach as a threat? Is it possible to be both a faithful member of a religious tradition and committed to questioning everything with logic?
The Byzantines preserved Aristotle’s logic while also believing in a God who created the world. Do you see any tension between believing in a creator God and believing that the categories we use to understand the world are real?

Where This Shows Up

In school: When your teacher talks about “classes” of animals or types of chemical elements, they’re using universals. The question is whether those categories exist in nature or are just human inventions.
In arguments: When people debate whether “fairness” or “justice” is a real thing or just a word we use, they’re arguing about universals.
In computer science: Programmers who design systems of categories (like “mammal” inheriting from “animal”) are dealing with the same problem of universals in a practical form.
In politics: Debates about whether groups like “the working class” or “the nation” are real entities or just convenient labels echo the Byzantine debate about the reality of universals.