What Does It Mean to Judge Something?

Imagine you’re standing in your kitchen. You see a red apple on the counter. You don’t think anything about it—you just see it. Now imagine someone asks you, “Is there an apple on the counter?” You look, and you say, “Yes.” That “yes” feels different from just seeing the apple, doesn’t it? It’s a kind of mental act—an acceptance that the apple is really there.

But what exactly happened in your mind when you said “yes”? Did you take the idea of “apple” and the idea of “exists” and stick them together like two Lego bricks? Or did you do something simpler—just acknowledge the apple itself?

This is the puzzle that the philosopher Franz Brentano spent years thinking about. And his answers turned out to be surprisingly strange and complicated.

The Basic Puzzle: What Is a Judgement?

Here’s the problem Brentano started with. You can have a thought about something without believing it’s real. You can imagine a purple elephant without thinking purple elephants exist. That’s called a presentation—just having an idea. But when you judge something, you’re doing something different. You’re either accepting it as true or rejecting it as false.

So far that sounds simple. But when philosophers tried to explain what judging actually is, they ran into trouble.

Most philosophers before Brentano thought that every judgement worked like this: you take two ideas (say, “apple” and “red”) and you either combine them (judging “The apple is red”) or separate them (judging “The apple is not red”). Judging was basically a kind of mental combining or separating.

Brentano thought this was wrong. And he had a clever argument to prove it.

Why Perception Breaks the Theory

Think about what happens when you perceive something. When you see a red apple sitting on the counter, you don’t first think “apple,” then think “red,” then combine them. You just see the apple. And yet, when you see it, you also know it’s there. You accept its existence.

Brentano pointed out that everyone—even the philosophers who thought all judgements were combinations of ideas—agreed that perception is a kind of judgement. When you see a sound or a color, you’re taking it to be real. But perception doesn’t feel like combining ideas. It feels like being in contact with something directly.

This gets complicated, but here’s what it accomplishes: Brentano showed that there must be some judgements that aren’t about combining two ideas. In fact, he thought the simplest kind of judgement is just acknowledging an object—saying “yes” to it—or rejecting it—saying “no” to it. No combination needed.

The Radical Move: All Judgements Are Really About Existence

Once Brentano had this idea, he pushed it further. He thought: maybe every judgement is really just acknowledging or rejecting the existence of something.

Consider the sentence “All humans are mortal.” According to Brentano, this doesn’t really mean “Every human has the property of being mortal.” Instead, it means “A non-mortal human does not exist.” The judgement is negative—it rejects the existence of something.

Consider “Some swans are white.” This becomes “A white swan exists.” The judgement is positive—it accepts the existence of something.

This is called the reduction thesis: every categorical judgement (the kind with a subject and predicate) can be translated into an existential judgement (the kind that says something exists or doesn’t exist). Brentano thought this revealed the true structure of our minds. Language was tricking us into thinking we were doing something complicated (combining ideas) when really we were doing something simple (accepting or rejecting objects).

The Problem with Negative Properties

But Brentano ran into trouble. And the trouble came from an unexpected place: negative properties.

Think about the judgement “Some humans are not mortal.” According to Brentano’s earlier theory, this means “A non-mortal human exists.” But what is a “non-mortal human”? It’s a human with the property of being non-mortal. And “non-mortal” is a negative property—a property that says what something isn’t rather than what it is.

Brentano didn’t like negative properties. He thought they were made-up, fictional things. When you say a rose isn’t black, you’re not saying the rose has the property of “being not-black.” You’re just denying that it’s black. The negation belongs to the act of judging, not to the content of what you’re judging.

But if that’s true, then his earlier theory was in trouble. When you judge “A non-mortal human exists,” you seem to be affirming the existence of something that includes a negative property. And Brentano couldn’t accept that.

The Double Judgement

So Brentano changed his mind. He developed what he called the theory of double judgement.

Here’s the idea. When you judge “Some S is P,” you’re actually making two judgements in one:

First, you acknowledge that S exists.
Then, after identifying P with S in your mind, you acknowledge S-with-P—you say “yes” to S as having the property P.

The two judgements are tied together, but they’re separate acts. And importantly, when you judge “Some S is not P,” something similar happens: you acknowledge S exists, and then you deny that S is P. The negation stays where it belongs—in the act of judging, not in the content.

This solved the negative property problem. But it also meant giving up on the idea that all judgements could be reduced to simple existential ones. Some judgements are genuinely complex. They involve acknowledging an object, and then saying something about it.

So What Does This Mean?

Brentano ended up with a theory that was messier than he’d hoped, but also more honest. He realized that our minds do different kinds of things when we judge. Sometimes we just accept or reject an object—that’s what happens in perception. Sometimes we make a double judgement—that’s what happens when we say things like “That apple is red.”

And this matters because it tells us something about how we relate to reality. When you judge, you’re not just rearranging ideas in your head. You’re committing yourself—saying “yes” or “no” to something real. The basic act of judgement is one of the most fundamental things your mind does, and Brentano showed that it’s stranger and more interesting than most philosophers had realized.

Nobody really knows whether Brentano got it exactly right. Philosophers still argue about whether there can be simple non-predicative judgements, or whether all judging involves combining ideas in some way. But Brentano’s central insight—that judgement is a distinctive kind of mental act, not reducible to having ideas or combining them—has influenced philosophers for over a century.

The next time you look at an apple and think “yes, it’s there,” you might wonder: what exactly did your mind just do? And whether Brentano was right that the simplest things we do are often the hardest to explain.

Key Terms

Term	What it does in this debate
Judgement	The mental act of accepting something as true or rejecting it as false
Presentation	Having an idea in mind without believing or disbelieving it
Existential judgement	A judgement that simply says something exists or doesn’t exist
Reduction thesis	The claim that all judgements can be translated into existential judgements
Double judgement	A complex judgement made of two parts: acknowledging an object, then saying something about it
Negative property	A property like “not-red” or “non-mortal”—which Brentano thought were fictional
Predication	Combining a subject and predicate in thought (like “apple is red”)

Key People

Franz Brentano (1838–1917): A philosopher who started as a Catholic priest, quit over church doctrine, and spent his career trying to understand how the mind works. He developed the theory of judgement described in this article.
Aristotle (384–322 BCE): An ancient Greek philosopher whose ideas about logic and judgement influenced everyone who came after. Brentano both admired and disagreed with him.
Immanuel Kant (1724–1804): A famously difficult German philosopher who argued that “exists” isn’t a real property of things. Brentano thought he was on the right track but didn’t go far enough.

Things to Think About

When you see something—like a tree outside your window—do you think you’re making a judgement? Or do you just see it? And how would you tell the difference?
Brentano thought that when you judge “Some humans are not mortal,” you’re not really saying anything about “non-mortal humans.” But if that’s true, what are you doing? Can you put it into words without using negative terms?
Is it possible to present something to your mind—just think about it—without making any judgement about whether it exists? Try it. Think about a unicorn. Did you end up judging something about it without meaning to?
Brentano’s theory changed over time. Is it better to have a simple, neat theory that doesn’t quite work, or a messy, complicated one that handles more cases? What makes a good theory?

Where This Shows Up

In psychology and neuroscience: Researchers still study how the brain distinguishes between simply perceiving something and making a judgement about it.
In computer science: When programmers try to build AI that can make judgements, they run into versions of the same problems Brentano faced.
In everyday arguments: When people disagree about whether something is true, they’re often also disagreeing about what kind of thing counts as evidence—which is a version of the question “what does it mean to judge correctly?”
In law: Courts have to decide what counts as someone “knowing” something versus just suspecting it—a distinction that connects back to the difference between presentation and judgement.