Thoughts on why answering metaphysical “What is X?” questions are possibly nonsense.

Last revised: 2025-08-12

Introduction

I’ve been involved in a bunch of conversations which try to determine the essence of something. For example:

• What is free will?
• Is the Conversation Game a social deduction game?
• Is cereal a kind of soup?

These all boil down to metaphysical questions of the form, "What is X?". For the question "Is cereal a kind of soup?", it will boil down to, "What is soup?", and will lead to a loop:

1. Alice lists properties that are common to what she thinks of as soup.

   “Soup has a liquidy base and maybe some other ingredients.”

2. Bob rebuts with some reason why Alice’s definition is not universal.

   “Then cereal in milk is soup!”

3. Bob proposes an alternate definition, also listing properties that are common to what he thinks of as soup.

   “Soup has a liquidy base and maybe some ingredients, that also must be savory.”

4. Alice rebuts with some reason why Bob’s definition is not universal.

   “Then tong sui is excluded, but saline solution is soup!”

5. Repeat 1-4 until one of various things happen:
   • Define soup too specifically and exclude lots of things which are intuitively soups.

     “Soup has a liquidy base, is edible, is hot, has bits in it, is savory, tastes good to at least one person…” → “Black sesame soup that has been in the fridge is not a soup.”

   • Attempt a middle-ground that is invariably too broad and includes things which are intuitively not soups.

     “Soup is a liquidy edible thing.” → “Cereal in milk is a soup.”

   • Give up on defining soup altogether and start talking about something else.

     “Did you see that ludicrous display last night?”

In this article, I propose that universal answers to these questions are impossible, and to come up with a definition to “What is an X?” requires you to compromise and create an answer that fails under at least one context.

Why there are no universal definitions

The big roadblocks to coming up with a one-size-fits-all definition for any word are:

1. The mental mismatch problem: whatever the word X is, X means different things to different people.
2. The context problem: words are context sensitive, so X can mean one thing in one context and something entirely different in another.

Problem 1: Mental mismatch

The easiest way to demonstrate the mental mismatch problem is using color:

This is barkleborp blue. Using only words, describe barkleborp blue to a random person in the street, and make sure they don’t confuse it with any other shade of blue, such as this blue, this blue, or this wigglewum blue that looks a lot like barkleborp blue but is actually slightly brighter.

Even if you were happy with your description, what happens when you try to describe this to someone who’s colorblind? Is the barkleborp blue that you see the same as their barkleborp blue?

Barkleborp blue, generalized

If you try to define “soup” in words, you will run into the same problem: you’ve seen, smelt, felt, and perhaps tasted many soups in your lifetime. Because of this, you have a mental idea of what soup is. Other people have seen, smelt, felt, and tasted soups also, but not the same soups that you’ve tasted, or in exactly the same way. Their idea of soup, similar as it may be, is not identical to yours.

This is how we learn all words: by relating it to our own experiences. Then, because everyone’s experiences are unique, then what those words mean to each person is also unique.

What about words for things I’ve never experienced?

Being told a definition for a word still requires you to relate that definition to your experiences. Click here for an example.

Even if you’ve never heard of a springbok before, if I tell you its Cambridge Dictionary entry:

“An animal found in Southern Africa that is reddish-brown with a white back end, has hoofs, and can jump very high.”

Then you’re relating information in the dictionary to your experiences:

• The springbok is an animal. They must have some similarities to other animals. What animals have you experienced?
• What do you know about Southern Africa? Have you been there? Maybe other people have told you about Southern Africa?
• A spingbok can jump very high. How high do you think high is?

In this case, how you understand this dictionary definition of springbok still depends on your lived experiences.

Problem 2: Context sensitivity

Non-compositionality: metaphors and set phrases

How is it possible to say anything at all?

That is not to say “soup” cannot be defined. Sometimes soup has a pretty concrete definition, like when you’re at a restaurant looking at soup section of the menu. In this context, “soup” refers to everything listed on the menu, and nothing that’s off the menu. But obviously, that definition only applies in the context of this particular restaurant.

The dictionary

How should “What is X” problems be approached?