Philosodata: Thought Experiments & Paradoxes

This is a list of philosophers’ thought experiments and paradoxes. They are distilled aspects of imagination designed to carve out very particular elements of understanding.

They’re usually implied as entertaining stories (and often the basis of many of them), but you’ll likely also see which philosophies you believe and why some laws are universal.

Others who are more visually creative than me (e.g., Nicky Case) have made better summaries, but this is a simplified distillation.

Types of thought experiments:

  • Prefactual – Given the present, what will happen in the future after an event happens? (pretty much what we do when making most decisions)
  • Counterfactual – What would happen if something had been hypothetically different? (aka alternate realities)
  • Semifactual – What would happen if everything was the exact same, but there was one difference in the situation? (alternate realities with variations)
  • Predictive – Assuming things we know right now, what will likely happen? (often used for scientific and marketing modeling)
  • Hindcasting – Assuming things we know and a prediction model, can we reproduce what happened inside the model? (typically used to test modeling)
  • Retrodiction – Going back in time step-by-step, what ultimately caused the event? (a common form of gaining wisdom)
  • Backcasting – Assuming a specific event in the future, what things step-by-step could have theoretically caused that event? (often used for lofty science fiction and fantasy)

If you start mixing math into your thought experiments, you’ve just swerved into the realm of game theory.

If you like thought experiments, you can make your own:

  1. Think of a commonplace situation in your own life.
  2. Draw out an extremely ridiculous circumstance off your situation.
  3. Imagine what you’d do in that situation.
  4. Make circumstances even more ridiculous until that decision is difficult to maintain.
  5. Publish that new, ridiculous impossible situation and call yourself a philosopher, or add math and call yourself a game theorist.

This is in no way an exhaustive list. Here’s a few of mine I’ve made simply by thinking about stuff:

  • The Accidental Arsonist – Is someone who caused untold damage and destruction responsible if they don’t know what they did?
  • The Amnesiac Arsonist – Is someone who purposely caused damage and destruction responsible if they’ve completely changed their ways from ever doing it again and don’t ever remember having done it?
  • The Hidden Break – If someone damages something you highly value without you knowing it, then completely repairs it to where you can’t tell, are they morally obligated to tell you?

Agrippa’s/Münchhausen’s Trilemma

Is it possible to base understanding on something that isn’t ultimately based on one of the 3 below sources?

  1. Circular reasoning, where the chain of reasoning goes in a circle.
  2. Regressive reasoning, where there’s an infinite chain of reasons.
  3. Dogmatic reasoning, which sits on things that don’t have reasoning behind them.

Or, to put more simply, is it possible to have a finite, perfectly sound and fully justified reasoning about anything?

Barber Paradox

If a barber shaves only those who don’t shave themselves, does a barber shave himself?

If a barber does shave himself, he’s no longer a barber. If a barber doesn’t shave himself, he’s part of the group of people who don’t shave themselves and therefore a barber to himself.


If everyone had a box containing what everyone says is a beetle, and each other person could only see their own beetle, would descriptions of that “beetle” matter to understand it?

How certain can anyone be of each others’ descriptions?

What if nobody has ever seen a beetle?

Without anything scientific to measure together, how sure could anyone be that those boxes could have non-beetles or simply be empty?

Gavagai Remix:

  • If a linguist discovering a foreign tribe learned of the word “gavagai” by seeing a tribal member point at a rabbit, will he understand later without extra information whether he’s referring to a rabbit, rabbit-parts, or a symbolic representation from rabbits when he says “gavagai” to tribe members later?

Buridan’s Ass

If someone were equally hungry and thirsty, and food and drink were placed an equal distance away, how would they know which one to go to, and why?

Would they even go, or simply die of hunger/thirst, and why?

If it’s a random nudge in one direction or another, what caused that nudge?

Collectivism Paradox

It’s good for everyone to share when there’s a surplus, but should there be a rule for mandatory sharing?

If everyone were required to share when there wasn’t enough to go around, is that oppressing the person who has barely enough to survive?

Is it better for everyone to suffer equally, or for some people to not suffer at all?

Evil God Challenge

Presuming the belief of a God, why do we believe an all-good God is more likely than an all-evil God?

Experience Machine

Psychologists have now invented a machine that can give pleasurable experiences which are completely indistinguishable from reality. If given the choice, would we prefer the machine to real life?

Even Firing Squad

If a firing squad of 6 shooters are accurately aiming at an innocent person’s heart, are any one of those people a murderer?

If they’re all 1/6 murderers, who is responsible? Does it matter whose bullet arrived first? What about if they didn’t want to kill that person?

Floating Man

If someone had no ability to perceive, floating in the air and unable to interact with anything else, would that person still acknowledge the existence of “self”?

If that person were able to imagine anything of their body, such as their hand, would they imagine that thing to be part of themselves without any context?

Grandfather Paradox

If you invented a time machine, could you go back in time and kill your grandfather?

If you did kill your grandfather, what would happen?

Infinite Monkeys Theorem

If you had an infinite amount of monkeys banging away randomly at a typewriter, eventually, given enough time, one of them would type a Shakespeare play by typing at random.

Given this fact, can this expand indefinitely? Can they create perfect order?

Can the universe itself come to exist from infinite randomness?

Inverted Spectrum

If you woke up one morning and all the colors were inverted (red is green, blue is orange, etc.), and you had no observable explanation of why, will your ideas of specific colors change as well?

What if everyone else didn’t note the colors changing? Would you still believe those ideas you held?

Irresistible Force Paradox

What happens when a completely unstoppable force meets a completely immovable object?

God’s Lifting Paradox:

  • Can God make a stone so large he can’t lift it?

Liar’s Paradox

The next statement is true.

The previous statement was false.

Epimenides’ Paradox Remix:

  • “All liars are always liars”, said the liar.

Omphalos/Five-Minute Hypothesis

If the world had been formed five minutes ago, with everything fully grown and looking as if it were aged, as well as everyone being created with memories and documents of historically recorded things, would there be any way to prove that the world was only five minutes old?

Lottery Paradox

There’s a completely fair lottery with 1,000 tickets where 1 ticket will win.

It’s completely rational to believe that something is very likely if it has over a 99% chance of happening.

Thus, it’s rational to believe Ticket 1 won’t win, and Ticket 2, and so on through Ticket 1,000. Therefore, it’s rational to believe that none of the tickets will win.

That’s obviously silly, but why?

Molyneux’s Problem

Imagine being born blind, and have been taught to distinguish between a cube and a sphere of the same metal by touch alone. Now, imagine newly gaining sight and a cube and sphere have been placed across the room from you. Do you have the means to discern which one is which without touching it or seeing it move?

Newcomb’s Paradox

You’re presented with two boxes.

Box A is clear, and has $1,000 in it.

Box B is opaque, and will either have nothing or $1,000,000 in it.

You must decide to take either Boxes B and A, or Box B by itself.

To determine Box B, someone/something else was predicting whether you’d choose both boxes or Box B. If it expected you to choose both boxes, there’s nothing in Box B, and if it expected you to only choose Box B there’s $1,000,000 in it.

Philosophical Zombie

If a being could be made that was completely identical to a normal person and responded the exact same way, but didn’t have any consciousness whatsoever of what it did, is it a human? If not, why?

Relativism Paradox

If something (a perspective, moral statement, observation) is completely relative, can you have any value statement about it that has any legitimate weight?

If you say something is absolute and someone else disagrees on equal terms with you, with equally valid logic and reasoning, how can you tell who is right?

Russell’s Teapot

If someone were to make the claim that a teapot that’s too small for telescopes to see was orbiting the sun, would everyone else have to prove that person wrong, or would that person have to prove that point?

Starving Marvin

Marvin is in desperate need of food, and has to walk to the local marketplace to buy bread. If there was no outside interference, his plan would succeed. Sam is aware of this and is watching Marvin, and decides to detain Marvin on the way to the marketplace. This causes Marvin to die.

Did this violate Marvin’s rights? Is Sam a murderer? If not, why?

Teletransport/Duplicates Paradox

If you could be transported by completely rebuilding the atomic structure of yourself using teleportation technology, would that physically new version of you still be “you”?

Now, what if the “original” you was never destroyed, or a backup version of “original you” was restored? Which version will be “you”?

Tormented/Content Philosopher/Fool

If you could possess all the wisdom of the universe and be tormented nonstop by it, or be a complete and utter fool but happy, which one would you be?

Matrix Remix:

  • If you could take a red pill that would show you the truth about reality, or a blue pill that kept you ignorant, which one would you take?

Sheep in the Field/Fake Barns

If you’re looking at a field and see what appears to be a sheep, but that sheep is in fact a dog disguised as a sheep, are you correct when you say, “I see a sheep”?

Now, what if you’re certainly not seeing a sheep, but there’s an actual sheep behind that fake sheep that you can’t see. Is your statement “I see a sheep” still true?

What if you think you see a barn, and it is in fact a barn’s facade, but it’s not a barn. Would your perceptions be accurate?

Theseus’ Paradox

Every time Theseus goes to port, he changes out a plank.

After enough years, his entire ship has been replaced by new planks.

Is his ship the same ship, or is it a new one?

If it’s a new one, when did the ship become new?


  • Over about 7 years’ time, every cell in our body is replaced. Are you the same person you were as of 7 years ago?

Toxin Puzzle

An eccentric billionaire makes a poison that will make you horrifically sick for a day, but won’t kill you or have long-term effects. He’ll give you a million dollars, transacted into your account at midnight, if you intend to drink the poison tomorrow afternoon. The billionaire also says you don’t need to actually drink the poison, and can change your intent after midnight.

Can you intend to drink the poison if you also intend to change your mind later?

Trolley Problem/Bystander at the Switch

You’re in a runaway trolley. Up ahead, 5 people are tied up and unable to move, and will certainly die if you don’t pull a lever. However, if you do pull that lever, the trolley will certainly kill 1 person standing on another track.

Do you do nothing and let 5 people die, or pull the lever and let 1 person die?

There are a ton of remixes of the Trolley Problem:

  • If you could instead push a fat guy onto the tracks that would stop the train, would you?
  • What if pulling the lever would only likely save the 5 people, but certainly kill the 1 person?

The Trolley Problem also assembles with more complexities:

  • If it was a government threatening to kill 2 people if you confessed to a crime you didn’t commit or 30 people if you didn’t, should you confess?

Even More Trolley Problems

Uselessness Question

Can you ever think of something that’s legitimately useless?

Since you’re answering that question, is that thing still useless?

Vertiginous Question

Of all the experiences and thoughts possible, why is yours the most “real”?

Wax Argument

Since water changes all its properties from solid, to melting, to steam, what is water itself? It’s certainly not the things we describe it to be (e.g., hard, transparent, warm) so where do we find its properties?

Zeno’s Paradox

If you go from Point A to Point B, you have to go halfway there (we’ll call it Point 1).

If you go from Point A to Point 1, you have to go halfway there (we’ll call it Point 2).

From Point A to Point 2, you have to go halfway there…

How can you logically prove that you actually go anywhere at all?

The same goes for time. How does “now” become “tomorrow”?