Can Making Up a Word Change What’s True?

The Game of Defining Words

Suppose you invent a word right now: skronkle. You decide it means “a creature that can fold itself into a perfect cube and roll downhill.” Have you just added something to reality, or only to your vocabulary? Philosophers have been puzzling over this for centuries. A definition can be stipulative—you just declare what a new word means, like naming a pet. It can be descriptive, trying to capture how people already use a term, like a dictionary entry. Or it can be explicative—improving a fuzzy everyday idea for a sharper purpose, the way a scientist defines “one meter” with a metal bar.

But the reason this matters in philosophy is much bigger. Thinkers like Gottlob Frege (1848–1925) and Bertrand Russell (1872–1970) believed that definitions could solve deep puzzles about knowledge. They wanted to show that all of arithmetic is really just logic in disguise, by defining numbers using only logical ideas. For them, a definition wasn’t just a label—it was supposed to be a key that unlocks a hidden connection. That ambition raised a sharp question: what rules must a definition follow to work as a key and not a trick?

To get a grip on that, John Locke (1632–1704) offered a useful distinction. A real definition, he said, tries to capture the inner nature of a thing—what gold really is, down to its invisible parts. A nominal definition captures the idea we attach to a word—gold is yellow, heavy, and shiny. A chemist aims at a real definition; a lexicographer aims at a nominal one. But when Frege and Russell tried to define numbers, they wanted something stricter: definitions that give us real knowledge without sneaking in new assumptions. That’s where the fight begins.

The Safety Rules: Don’t Invent New Truths

If definitions can unlock knowledge, they can’t be allowed to just invent facts out of nowhere. Imagine defining a “shmoogle” as “a winged horse that lives in your garage and grants wishes.” That definition doesn’t make a shmoogle real. Most philosophers agree a definition must obey two basic safety rules.

The first is Conservativeness: adding a definition shouldn’t let you prove anything new about the world that you couldn’t prove before. If I can prove, using only your definition, that there are at least seventeen objects in the universe, something has gone wrong—definitions are not supposed to be magic spells. The second rule is Eliminability: any sentence that uses the new term should be translatable into a sentence that doesn’t use it, without changing its truth. Think of it like building with Lego. You can introduce a new named piece, but you must be able to describe the whole model using only the original bricks. If the new piece secretly added a new shape that wasn’t in the box, you’ve cheated.

These rules lead to a neat system, often called the traditional account. It says definitions must take a normal form. For example, if you define a name like “the roundest planet in this solar system,” you must first prove that exactly one such planet exists. That way the definition doesn’t smuggle in any existence claims that aren’t already backed up. And for a predicate like “is a zoggin” (where a zoggin is a rational, imaginative being), the definition just gives a condition; it doesn’t force you to believe zoggins actually exist. The traditional rules feel like common sense—and for a long time they held the field.

When Definitions Seem to Create Reality

But what if a definition, just by being written down, seemed to make a new truth pop into existence? That’s the challenge posed by implicit definitions. Instead of giving a single defining phrase, an implicit definition lays down a whole theory, and says: the term means whatever satisfies this theory.

A famous example is Hume’s Principle, named after David Hume (1711–1776) but used by Frege. It says: the number of Fs equals the number of Gs exactly when you can pair up each F with a unique G, with none left over. This principle looks like a definition of “the number of.” And it seems to let you prove that there are infinitely many objects—something you couldn’t prove before. That violates Conservativeness. A group of philosophers called neo-Fregeans argues that this is fine: the definition fixes the meaning of “number” even if it generates new truths. It’s a legitimate implicit definition, not a trick.

Many other philosophers disagree. They point to the Bad Company problem: some principles that look just like Hume’s Principle, when put together, produce logical contradictions. Conservative definitions never misbehave this way. So relaxing the safety rules risks letting in nonsense along with meaning. The debate is still wide open: can some definitions genuinely add to what there is, or must every definition merely recycle old facts in a new package?

The Troublemaker: Definitions That Loop Around

There’s an even more radical challenge. What if a definition uses the very word it’s supposed to define? A definition like “a liar is someone whose every statement is false” seems to circle back on itself. If that person says “I am a liar,” you get a famous paradox. Bertrand Russell thought such circular definitions were meaningless. He proposed the Vicious-Circle Principle: a definition can’t refer to a collection that includes the very thing being defined. Otherwise, he argued, you build a logical trap.

But some contemporary philosophers, especially Anil Gupta (20th–21st century), take the opposite view. They developed the revision theory of definitions. The idea is this: a circular definition doesn’t give you a fixed list of things that satisfy it. Instead, it gives a rule of revision—a recipe for improving your best guess. Start with a guess about what the new term applies to. Apply the rule, and you get a new, usually better guess. Keep applying it. For many objects, the process may settle: a certain object always ends up in the “yes” pile no matter where you started. For others, the answer might flip forever, or depend on your first guess—those are pathological cases. But the definition still provides a guide to use, just not a sharp boundary.

On this view, circular definitions can be perfectly meaningful. They meet Conservativeness—they don’t create new facts in the ground language—but they violate Eliminability, because you can’t reduce all their uses to non-circular terms. The revision theory shows that a concept like truth, which often behaves in a circular way, might work like this. So instead of a single set of safety rules, we now have two rival pictures: the traditional, straight-line account and the revisionist, looping one.

Why Your Definitions Matter More Than You Think

It might sound like a dusty quarrel about grammar and math. But these arguments touch your life directly. Whenever a new law defines “personhood,” a school defines “plagiarism,” or friends argue about what counts as “fair,” they’re doing philosophy. If you accept only the traditional safety rules, you’ll insist that no definition can sneak in new rights or obligations unless they’re already built into the old concepts. If you think implicit definitions can be creative, you might allow that a new definition of “family” can genuinely expand who counts. And if you’re open to circular definitions, you might recognize that some of our most important ideas—like truth, justice, or coolness—never quite settle into a neat checklist.

Understanding these hidden rules makes you a sharper thinker. You can spot when someone is trying to win an argument by defining a word in a loaded way. You can ask whether a definition is truly conservative or whether it’s quietly adding something new. Most of all, you see that language is not a passive mirror of the world; it’s a tool we wield, with power and limits. So the next time you make up a word like “skronkle,” you’re not just playing. You’re stepping into a conversation that stretches from Locke’s study to the edge of modern logic.

Think about it

1. If you invent a word “flump” and define it as “a creature that becomes invisible the moment nobody is looking,” does your definition make flumps real? What could it mean to say the definition is “good” even though no flump has ever been seen?

2. Suppose a group defines “cheating in a game” as “any action that increases your chances of winning beyond pure luck and skill.” Could you object that this definition is circular in a bad way, or that it secretly changes the meaning of cheating so that even drinking water before a race counts? How might the safety rules help you evaluate it?

3. A circular definition says: “A ‘true friend’ is someone whom true friends would trust.” If you used the revision theory’s method—starting with a guess and applying the rule over and over—do you think the process would ever settle? Why might some people end up with different stable answers?