Riddles With No Answer

Five riddles with no answer: talk each one over, then tap Show reason to see why none is settled.

If a tree falls in a forest and no one is around to hear it, does it make a sound?
One grain of sand is not a heap. Adding one grain to something that is not a heap never makes it a heap. So how did the pile on the beach become a heap?
Is there a largest prime number?
A room has four corners. In each corner sits nobody, and nobody stands in the middle. How many people are in the room?
A customer asks how much a new house costs, and the builder replies: 'How long is a piece of string?' What is the builder saying?

Next step Yes or no riddles for a table Philosophical questions to talk over

How it works

Some riddles with no answers were never meant to have one, and some have been argued over for two thousand years. These are the unsolvable riddles, each with the reason under a cover.

Read the full guide

Four sets, from unanswerable riddles to the answer no

The menu under the button keeps one set. Famous unanswered riddles are questions people still ask. In Paradoxes told as riddles every step looks right and the end cannot be. Old teaching questions come from Zen, ancient China, Greece and the Jewish tradition. The answer is no or nothing has an answer after all.

A page for talking, not for scoring

Read one aloud and let the room argue. Show reason opens what people have said about it and why nothing is settled.

Tips

Have everyone pick a side before the cover opens, then argue the other side for one minute.

Questions and answers

What are riddles with the answer of no?

Riddles whose honest answer is no, none or nothing. Take one step north from the North Pole: where are you? Nowhere new, because no north is left. What is the last digit of pi? There is none. The fourth set holds ten of them.

Are zen koan riddles really riddles?

Not in the usual sense. A koan is a question from Zen Buddhist training, such as the sound of one hand. A student works on it with a teacher, and it is not a puzzle to solve, so this page prints no answer.

What is the most famous riddle with no answer?

Probably the Hatter's: why is a raven like a writing desk? In the book nobody knows, and the author wrote years later that the riddle, as first invented, had no answer at all.

Is an unsolvable riddle the same as a very hard riddle?

No. A hard riddle has one answer that is difficult to find. The riddles here have no answer that is agreed, or the question itself breaks down when you follow it, which is what makes a paradox.

All 37 riddles

Famous unanswered riddles 8

A customer asks how much a new house costs, and the builder replies: 'How long is a piece of string?' What is the builder saying? Why there is no answer: The saying is used on purpose when a question cannot be answered until more is known. Any length is the right one for some piece of string, and any price for some house.
How many angels can dance on the head of a pin? Why there is no answer: Nobody expects a count. The question is used as a picture of time spent arguing over things of no practical value, and it is quoted to tease a debate that has drifted away from anything that can be checked.
How much wood would a woodchuck chuck if a woodchuck could chuck wood? Why there is no answer: It is a tongue twister from a song of 1902, and the usual reply only hands the question back: as much wood as a woodchuck could chuck. In 1988 a wildlife technician in New York offered a playful figure of about 700 pounds, worked out from the dirt a woodchuck moves when it digs a burrow.
If a tree falls in a forest and no one is around to hear it, does it make a sound? Why there is no answer: It depends on what the word sound means. If a sound is a movement of the air, the tree makes one. If a sound is something that is heard, it does not. Both meanings are in everyday use, so both answers can be defended.
Is the glass half empty or half full? Why there is no single answer: Both descriptions fit the same glass. The question is asked to show whether a person tends to look at things hopefully or gloomily, and the water has no say in it.
The old question asks whether the first chicken came before the first egg, or the first egg before the first chicken. Which was it? Why there is no simple answer: Taken as it is meant, every chicken came out of an egg and every chicken egg out of a chicken, so neither can be first. Aristotle took it for a chain with no first link. Biologists do give a literal answer, the egg, because eggs are far older than chickens. The phrase lives on as the name for any problem in which each thing seems to need the other first.
Where does a circle begin, and where does it end? Why there is no answer: A circle has no corner and no end point. Any point on it can serve as the start, and none has a better claim than another.
Why is a raven like a writing desk? Why there is no answer: The Hatter asks this at the tea party in Alice's Adventures in Wonderland (1865), and when Alice gives up he says he has not the slightest idea. Lewis Carroll wrote years later that the riddle, as first invented, had no answer at all. As an afterthought he offered one: because it can produce a few notes, though they are very flat.

Paradoxes told as riddles 10

A donkey that always walks to the nearer pile of hay stands exactly halfway between two equal piles. Which pile does it eat? Why there is no answer: By its own rule the donkey can choose neither. The puzzle is known as Buridan's ass, and it is used to ask whether a choice can be made when there is no reason to prefer one side.
A predictor who is almost never wrong sets out two boxes. The open one holds a thousand dollars. The closed one holds a million, but only if she predicted that you would leave the open box behind. Both boxes are already filled. Do you take both, or only the closed one? Why there is no settled answer: This is Newcomb's problem. One side says to take both: the boxes are already filled, and both is always a thousand more. The other side says that the people who take one box are the ones who find a million in it. Robert Nozick, who wrote about it in 1969, found that people divide almost evenly, each half sure that the other is being silly.
A sign on the wall says: 'This sign is false.' Is the sign true or false? Why there is no answer: If the sign is true, then it is false, as it says. If it is false, then what it says is so, and it is true. This is the liar paradox, a puzzle from ancient times, and logicians still disagree about the way out.
A traveler goes back in time with a book of songs and hands it to the young composer, who copies the songs out and becomes famous for them. Years later the traveler buys that very book and sets off. Who wrote the songs? Why there is no answer: Nobody did. This is a causal loop, also called the bootstrap paradox: the songs go around the loop and their origin cannot be found. Puzzles like this one are often raised against the idea of traveling into the past.
An old story says that the world rests on the back of a giant turtle. What is the turtle standing on? Why there is no answer: The joke reply is another turtle, and under that one another: turtles all the way down. The phrase is used for an infinite regress, an explanation that needs another explanation of the same kind beneath it, without end.
Answer this with yes or no, and answer truthfully: 'Is your answer to this question no?' Why there is no answer: Say yes, and your answer is not no, so yes was false. Say no, and your answer is no, so the true reply was yes. It is a cousin of the liar paradox: a question that turns on its own answer.
One grain of sand is not a heap. Adding one grain to something that is not a heap never makes it a heap. So how did the pile on the beach become a heap? Why there is no answer: Every step looks right, and the end is wrong. This is the paradox of the heap. The trouble seems to lie in words such as heap, tall and old, which have no sharp edge, and there is no agreed repair.
The sun has come up every morning so far. What proves that it will come up tomorrow? Why there is no settled answer: This is the problem of induction, set out by David Hume in 1739. Any argument that the future will be like the past seems to rest on the past having been a good guide so far, which is the very thing in question. Philosophers have offered many ways out, and none has been accepted by the rest.
What happens when a force that nothing can stop meets an object that nothing can move? Why there is no answer: The question describes two things that cannot both exist. If some force cannot be stopped, then nothing is immovable, and the other way around. It is known as the irresistible force paradox.
You know that the monster in the story is not real. So why does your heart pound when it starts up the stairs? Why there is no settled answer: This is the paradox of fiction, set out by the philosophers Colin Radford and Michael Weston in 1975. People seem to feel real fear and real pity for things they know do not exist, and how that can be has been argued over ever since.

Old teaching questions 9

A man dreamed that he was a butterfly, fluttering about and happy. When he woke, he asked: am I a man who dreamed of being a butterfly, or a butterfly now dreaming of being a man? Why there is no answer: The story is the butterfly dream in the Zhuangzi, a Chinese book more than two thousand years old. The book gives no answer, and how anyone can tell waking from dreaming is still asked.
A student asked the teacher Zhaozhou: 'Does a dog have Buddha-nature?' He answered with one word, wu, which is read in Japanese as mu. What did he mean? Why no answer is printed here: This is the first case of the Gateless Gate, a collection of Zen koans from the 1200s. The word means roughly not, or without. Students in the tradition work on it with a teacher, often as the first koan they are given.
Can you step into the same river twice? Why there is no settled answer: The saying that you cannot is credited to the Greek thinker Heraclitus. The water has moved on, and so have you. Whether it is still the same river is a question about what makes a thing the same thing over time.
How can you search for something when you do not know what it is? If you know it, you have no need to search. If you do not, how will you know it when you find it? Why there is no settled answer: This is Meno's paradox, from a dialogue by Plato. Socrates replies that learning is a kind of remembering, and readers have argued about that reply ever since.
If I do not look after myself, who will? If I look after only myself, what am I? And if not now, when? Why there is no one answer: These are three questions of Hillel the Elder, a Jewish teacher of about two thousand years ago, retold here in our words. They are asked of oneself, and each person's answer is their own.
Is a white horse a horse? An old argument says it is not: ask for a horse and a brown one will do, but ask for a white horse and it will not. Where does the argument go wrong, if it does? Why there is no settled answer: This is the White Horse Dialogue of the Chinese thinker Gongsun Long, more than two thousand years old. Readers still disagree about whether it makes a serious point about words or ties a knot on purpose.
Two friends stand on a bridge. One says: 'See how the fish dart about. That is what fish enjoy.' The other says: 'You are not a fish. How do you know what fish enjoy?' Who is right? Why there is no answer: This is the debate on the joy of fish in the Zhuangzi. The first friend turns the question around: you are not me, so how do you know what I know? The book leaves the two of them on the bridge.
Two hands clap, and there is a sound. What is the sound of one hand? Why no answer is printed here: This is a koan from Zen Buddhism, used by the Japanese teacher Hakuin Ekaku, who lived from 1686 to 1769. Many people take a koan for a question that cannot be answered. In Zen practice it is not a riddle or a puzzle: a student works on it with a teacher, who expects a response.
What did your face look like before your parents were born? Why no answer is printed here: This is a koan from Zen Buddhism, known as the original face. A question about the original face stands in case 23 of the Gateless Gate, a collection from the 1200s. A student works on it in training, with a teacher, so there is no answer for a page to hand out.

The answer is no or nothing 10

A room has four corners. In each corner sits nobody, and nobody stands in the middle. How many people are in the room? Answer: None. Nobody in every corner and nobody in the middle is nobody at all.
Can a triangle drawn on flat paper have two right angles? Answer: No. The three angles of a flat triangle add up to 180 degrees, and two right angles would use up all of it.
I am what is left in the jar when the last cookie is gone, what a locked diary tells a stranger, and what you hear in a sealed and empty room. What am I? Answer: Nothing. An empty jar holds nothing, a locked diary tells nothing, and an empty room says nothing.
Is there a largest prime number? Answer: No. There are infinitely many prime numbers, a result known as Euclid's theorem.
Is this sentence a statement? Answer: No. It asks something and ends with a question mark, so it is a question.
Stand at the North Pole and take one step north. Where are you now? Answer: Nowhere new. The North Pole is the northernmost point on the Earth, so there is no north left to step into: every step from there goes south.
What do you get when you share ten apples among zero people? Answer: No answer at all. Arithmetic leaves division by zero undefined: no number of apples each makes sense when there is nobody to hand them to.
What is the biggest number? Answer: There is none. Name any number, and that number plus one is bigger.
What is the last digit of pi? Answer: There is none. The digits of pi after the decimal point never come to an end.
Who sits at the head of a round table? Answer: Nobody. A round table has no head, which in the old stories is why King Arthur's knights sat at one: everyone there had equal standing.

How this list was compiled

Written by the Game Night Generator editors on October 3, 2026: 37 riddles and questions that have no settled answer, in four sets, with the reason under each cover. Everything is retold in the editors' own words. The raven riddle was read on October 3, 2026 in chapter 7 of Alice's Adventures in Wonderland at Project Gutenberg (gutenberg.org, public domain), and its author's later note as quoted in the English Wikipedia article on the Hatter. The liar, the heap and the yes-or-no question were read in the Stanford Encyclopedia of Philosophy (plato.stanford.edu); the other paradoxes, the old teaching questions and the facts behind the last set in the English Wikipedia articles on each (en.wikipedia.org, text under the Creative Commons Attribution-ShareAlike license), and one saying in Wiktionary. Three of the teaching questions are koans from Zen Buddhism, which is a living religious practice: each is given with where it comes from and with no answer, because in Zen practice a koan is not a riddle or a puzzle but something a student works on with a teacher. One is a saying of Hillel the Elder, retold and not quoted from a translation. This site is not connected with Wikipedia, Project Gutenberg or the Stanford Encyclopedia of Philosophy. Licence: own work