Grelling–Nelson Paradox

Simple Definitions of the Grelling–Nelson Paradox

Imagine you have a box labeled “Things That Are Not Boxes.” The question is: can this box contain itself? If it can, then it no longer fits the label because it’s no longer something that is not a box. However, if it can’t contain itself, it does fit the label, but we have a problem because it should be able to contain things that are not boxes. This puzzle is similar to what happens in the Grelling–Nelson Paradox, but with words instead of boxes.

Here’s another way to look at it: If someone asks you to say a word that does not describe itself and you say “purple” because the word purple is not actually the color purple, then you’re following the rules. But if you say the word “word,” does it describe itself? Yes, because a word is a word. The Grelling–Nelson Paradox challenges us with one tricky adjective, “heterological,” which means an adjective that does not describe itself. The paradox is figuring out if “heterological” is or is not heterological. Each time you try to decide, you end up flipping back and forth between answers.


The Grelling–Nelson Paradox came to life when two thinkers, Kurt Grelling and Leonard Nelson, stumbled upon it in 1908. They were part of a group called the Berlin Circle which loved to dig deep into logical and language puzzles. This brain twister they created is like a cousin to other paradoxes that deal with statements that turn back on themselves, like the famous “liar paradox” which is about a sentence saying “this sentence is false.” It makes us wonder about how words that talk about themselves can mess with our heads and challenge the rules of language.

Key Arguments

  • The paradox shows us how tricky it can be when words or expressions point to themselves.
  • It questions the simple split of adjectives into two groups: those that describe themselves and those that don’t.
  • It suggests there might be something fundamentally flawed with how we try to neatly label parts of language.
  • The Grelling–Nelson Paradox uncovers possible limits in our language rules and logical thinking.

Answer or Resolution (if any)

Cracking the code of the Grelling–Nelson Paradox has been tough for brainy types like philosophers and logicians. Some think this conundrum hints that we can’t neatly fit language into boxes without running into trouble. For example, Alfred Tarski’s idea to separate languages into levels—one for talking and another for talking about talking—helps to steer clear of such brain teasers. Even though there’s no final solution yet, this paradox has sharpened our thinking and strategies for tackling language and logic.

Major Criticism

A big critique of the Grelling–Nelson Paradox is that it might just be about mixing up different levels of chat. By keeping regular talk and talk-about-talk in their own lanes, the whole paradox might just melt away. This idea comes from Alfred Tarski, who suggested sorting languages into different levels to avoid looping back onto themselves.

Practical Applications (if any)

  • Programming Languages: Computer science brains find this helpful to stop puzzles in coding languages from causing errors or security issues.
  • Mathematics: In math, especially with sets and logic, the paradox’s ideas about loop-de-loop systems help build more solid foundations.
  • Philosophical Analysis: Big thinkers dig into the paradox because it tackles deep questions about meaning, words, and how we construct thoughts.


The Grelling–Nelson Paradox is a riddle that has teased some of the smartest minds out there. Even though it might seem like just a head scratcher for fun, it actually touches on crucial points about how we use language, loop back on what we say, and how we try to sort things into categories. This is especially important in areas where details are key. The paradox is more than just a party trick; it’s a spotlight on potential issues with the way we figure out and use our language and logic. It also nudges forward new ideas and systems that can manage the tricky parts of self-referencing without tripping over themselves. The ongoing conversation about this paradox highlights the deep effect that puzzles in language and logic can have on the way we see the world and figure ourselves out.

Related Topics

There are a few other brain twisters out there that get along with the Grelling–Nelson Paradox. Here are some of them:

  • The Liar Paradox: As mentioned before, this one is about a sentence that says “this sentence is false,” which flips back and forth between being true and false.
  • Russell’s Paradox: This deals with sets in math that can’t contain themselves and challenges the very roots of set theory.
  • Cantor’s Diagonal Argument: This is a clever math proof by Cantor that shows there are different sizes of infinity, which stretches our brains in similar ways to the Grelling-Nelson Paradox.

Understanding these related topics can give us insights into the nature of language, logic, and even infinity. They all show how trying to neatly organize things can lead to puzzles that aren’t just black and white.