• 150 questions

Abstract Philosophy Questions and 25 Thought Experiments

One abstract question at a time, with a follow-up that pushes the first answer further.

Abstract Philosophy Questions and 25 Thought Experiments

Where does your lap go when you stand up?

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What else exists only while you sit? Funny.

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All 150 questions

Knowledge and reality 22

  • A brain floats in a vat while a computer feeds it a perfect world. What, if anything, could that brain come to know? Follow-up: What would the word tree mean to a brain that never met one? The brain in a vat: Hilary Putnam, Reason, Truth and History (1981).
  • Descartes sat by his fire, sure he was awake, then recalled dreaming that very scene. How can anyone tell they are awake right now? Follow-up: What test could a dream not fake? The dream argument: René Descartes, first Meditation.
  • How can a person be certain and wrong at the same moment? Follow-up: What does certainty feel like from the inside, then?
  • How do you know the fridge light goes off when the door shuts? Follow-up: What else do you believe only because the alternative would be odd? Funny.
  • If a theory predicts everything correctly, what more could it mean to call it true? Follow-up: What if two rival theories both predict everything?
  • If a wild rumor turns out to be true, was the person who spread it right or just lucky? Follow-up: What do we owe someone who was right by accident? Funny.
  • In what sense does money exist? Follow-up: What else exists only because people agree that it does?
  • Prisoners chained in a cave see only shadows on a wall and take them for the world. What might our shadows be? Follow-up: How would someone who had been outside convince the rest? Plato's Cave: Plato, Republic, book 7.
  • Were numbers discovered, like a continent, or invented, like chess? Follow-up: What would an alien's arithmetic share with ours?
  • What could a mind know without ever having had a single experience? Follow-up: Where would logic and arithmetic come from?
  • What does every map leave out that the territory has, and can any description avoid that? Follow-up: What is language a map of?
  • What is something everyone knows that nobody has ever checked? Follow-up: What would checking it take?
  • What is the difference between believing something and knowing it? Follow-up: Where does being very sure fit in?
  • What is the least you could know about a subject and still win an argument about it? Follow-up: What does that say about arguments? Funny.
  • What makes a fact different from an opinion that everybody shares? Follow-up: Which opinions of today will look like errors in 200 years?
  • What makes something real: that you can touch it, that it has effects, or something else? Follow-up: Where does that leave a rainbow, a promise or a Tuesday?
  • What separates a good explanation from a story that merely feels satisfying? Follow-up: Which popular explanation fails that test?
  • When two careful people weigh the same evidence and disagree, what should each do next? Follow-up: How much should it matter which one is the expert?
  • Why give the simplest explanation a head start, if the world has no duty to be simple? Follow-up: When has the complicated answer been the right one?
  • Why trust your senses, when every test of them uses your senses? Follow-up: Which sense would you doubt last?
  • With no mind anywhere to observe it, would the world be colored, silent or neither? Follow-up: Where does color live, in the apple or in the eye?
  • You glance at a stopped clock at the one minute it happens to be right. Do you know the time, or did you only get lucky? Follow-up: What has to be added to a true belief to make it knowledge? The stopped clock: Bertrand Russell.

Mind and consciousness 22

  • A bat finds its way by echo. What could a human ever know about what being that bat is like? Follow-up: What would a bat fail to grasp about being you? What is it like to be a bat: Thomas Nagel (1974).
  • A man born blind knows a cube from a sphere by touch. If he could suddenly see, how would he tell which is which without touching them? Follow-up: What does your answer say about where the idea of shape comes from? Molyneux's problem: William Molyneux, in a letter to John Locke (1688).
  • A man who knows no Chinese follows a rulebook so well that his written replies fool native speakers. Who or what understands Chinese? Follow-up: What would have to be added before real understanding appeared? The Chinese room: John Searle, Minds, Brains and Programs (1980).
  • How could two people find out whether red looks the same to both of them? Follow-up: If it never makes a difference, does the question mean anything?
  • How do you know anyone else has an inner life like yours? Follow-up: What would count as evidence?
  • If chips replaced your neurons one at a time, at what point would the mind go out? Follow-up: What does your answer imply about what minds are made of?
  • If your phone remembers everything for you, how much of your mind is in your pocket? Follow-up: What happens to you when the battery runs out? Funny.
  • In what way can a feeling be mistaken, the way a belief can? Follow-up: What would correct it?
  • Mary knows every physical fact about color but has lived in a black-and-white room. What does she learn when she first sees red? Follow-up: If she learns something, what kind of fact was missing? Mary's room: Frank Jackson, Epiphenomenal Qualia (1982).
  • What does it mean to change your mind, and who is doing the changing? Follow-up: What stays the same while it changes?
  • What does it tell us that nobody can tickle themselves? Follow-up: What else can a mind not do to itself? Funny.
  • What is a dog thinking about when it stares at a blank wall? Follow-up: How would anyone ever check? Funny.
  • What is a pain, apart from how it feels and what it makes you do? Follow-up: How could something be in pain and show no sign of it?
  • What is the difference between a brain and a mind? Follow-up: Which one are you?
  • What is the difference between remembering an event and imagining it? Follow-up: How would you tell from the inside?
  • What work is consciousness doing that a very good autopilot could not do? Follow-up: Then why do we have it?
  • What would a machine have to do before you would say it feels something? Follow-up: Why is that the right test?
  • What would be lost if people could read each other's minds perfectly? Follow-up: What is privacy of thought for?
  • When you talk to yourself, who is listening? Follow-up: Which of the two is in charge? Funny.
  • Where is a thought while you are thinking it? Follow-up: What size or speed does it have?
  • Which animals have minds, and where would you draw the line? Follow-up: What puts an octopus above or below it?
  • Why should any physical process come with an inner experience at all? Follow-up: What would the world lose if it did not?

Free will 20

  • A hidden device would force Jones to pick A if he wavered. He picks A unprompted and it never fires. How responsible is he, if he could not have done otherwise? Follow-up: What does blame need: other options, or just owning the choice? Frankfurt's case: Harry Frankfurt, Alternate Possibilities and Moral Responsibility (1969).
  • A sleeping man is carried into a locked room with someone he longs to see, wakes and gladly stays. How free is his staying, when he could not leave? Follow-up: Which matters more, wanting what you do or being able to do otherwise? Locke's locked room: John Locke, Essay Concerning Human Understanding, II.xxi.10.
  • How free is a choice made under advertising, fashion and the wish to fit in? Follow-up: What would a choice with no influences even look like?
  • How much credit does anyone deserve for talents they were born with? Follow-up: And for the drive to work hard?
  • How should punishment change if nobody could ever have done otherwise? Follow-up: What is punishment for, then?
  • How would a purely random choice be any freer than a determined one? Follow-up: What third option is there?
  • If everything is determined, since when was this conversation going to happen? Follow-up: And was that last joke unavoidable? Funny.
  • If someone could predict your every move, what would that take away from you? Follow-up: What if they never told you?
  • If upbringing and genes shape every choice, what is left to praise or blame? Follow-up: Why do we still do both?
  • If you could only ever want what you did want, in what sense was the wanting yours? Follow-up: Whose else could it be?
  • Picture a mind that knows where every atom is and every force on it. If it can compute all that comes next, in what sense is the future open? Follow-up: What would be left for a choice to do? Laplace's demon: Pierre-Simon Laplace, Philosophical Essay on Probabilities.
  • What is a cat exercising when it pushes a glass off the table while holding your gaze? Follow-up: What would a jury of dogs decide? Funny.
  • What is a habit: a choice you keep making, or a choice you stopped making? Follow-up: How does a person get the choice back?
  • What is the difference between a choice that was caused and a choice that was forced? Follow-up: Which kind is more common?
  • What is willpower, and why does it run out? Follow-up: Who is resisting whom?
  • What would anyone do differently tomorrow on learning that free will is an illusion? Follow-up: If nothing, what was the belief doing?
  • When you pick a number between one and ten, where does the answer come from? Follow-up: How would you know you could have picked another?
  • Who decided on that second cookie, you or the cookie? Follow-up: What would your defense be in court? Funny.
  • Why do we excuse a sleepwalker and not a person who acts in anger? Follow-up: Where exactly is the line between them?
  • Why does a decision often feel made before you can give the reasons for it? Follow-up: Are the reasons the cause, or the press release?

Right and wrong 22

  • A machine can give you any experiences you choose, and once inside you will not know it is a machine. What reason is there to stay out? Follow-up: What do we want from life besides how it feels? The experience machine: Robert Nozick, Anarchy, State, and Utopia (1974).
  • A man finds a ring that makes him invisible. With no chance of being caught, what reason is left to be honest? Follow-up: What does your answer say about why people behave well? The ring of Gyges: told by Glaucon in Plato's Republic, book 2.
  • A runaway trolley is heading for five people. You can turn a switch that sends it toward one. What is the right thing to do, and why? Follow-up: What changes if stopping it means pushing a bystander onto the track? The trolley problem: Philippa Foot (1967), developed by Judith Jarvis Thomson (1985).
  • Are people kind by nature, or taught to be? Follow-up: What would a child raised by nobody be like?
  • How guilty should a person feel for laughing at a joke they wish they did not find funny? Follow-up: Is laughing a choice? Funny.
  • How many good deeds cancel out taking the last slice without asking? Follow-up: Who keeps the ledger? Funny.
  • If a wrong act leads to a better world, what is left of its wrongness? Follow-up: Who is still owed an apology?
  • If ants had a moral code, what would its first rule be? Follow-up: Which of our rules would baffle them? Funny.
  • If morality differs between cultures, what makes moral progress possible? Follow-up: Progress toward what?
  • What could make an act wrong if it harms nobody and nobody ever finds out? Follow-up: Who is wronged?
  • What do humans owe to animals, and why that much and no more? Follow-up: What would change the answer?
  • What do we owe to people who have not been born yet? Follow-up: How far ahead does the debt run?
  • What is the difference between being good and being nice? Follow-up: Which would you rather your friends were?
  • What is the moral difference between doing harm and letting it happen? Follow-up: Does the difference survive a hard case?
  • What makes a life go well: pleasure, getting what you want, or something else? Follow-up: Who gets to say what the something else is?
  • What makes a rule a moral rule and not just a custom? Follow-up: Which custom do people mistake for a moral rule?
  • When is breaking a promise the right thing to do? Follow-up: What is a promise worth, then?
  • Where do right and wrong come from, if not from whoever is in charge? Follow-up: Would they still hold if everyone voted against them?
  • Which is worse, a harmful act with good intentions or a harmless act with bad ones? Follow-up: Which of the two people would make the better neighbor?
  • Why does luck in how things turn out change how much we blame someone? Follow-up: Should it?
  • Would people behave better or worse if lying were impossible? Follow-up: Which lies hold things together?
  • You pass a shallow pond where a small child is drowning; wading in will muddy your clothes. If you must help here, why not a child far away? Follow-up: What difference does distance make to a duty? The drowning child: Peter Singer, Famine, Affluence, and Morality (1972).

Identity and the self 22

  • A band has replaced every member. What separates its reunion tour from a tribute act? Follow-up: Which member was the band? Funny.
  • A general recalls his days as a young officer. The officer recalled his boyhood, but the general has forgotten it. What makes general and boy one person? Follow-up: What besides memory could tie them together? The brave officer: Thomas Reid (1785).
  • A machine scans you, destroys the original and builds an exact copy on Mars, memories and all. Who steps out on Mars? Follow-up: What if the original were left standing? The teletransporter: Derek Parfit, Reasons and Persons (1984).
  • A prince wakes in a cobbler's body with all his princely memories. Who is he now, the prince or the cobbler? Follow-up: Who should be held to the prince's promises? The prince and the cobbler: John Locke, Essay Concerning Human Understanding, II.xxvii.15.
  • A ship has every plank replaced, one at a time. Then someone rebuilds the old planks into a second ship. Which one is the original? Follow-up: What if the same were done to a person, cell by cell? The ship of Theseus: reported by Plutarch; the second ship was added by Thomas Hobbes.
  • After total amnesia, what would become of the promises you made before it? Follow-up: Who made them, in law and in truth?
  • At what point does a sock with a mended heel, toe and cuff become a different sock? Follow-up: And what happened to the old one? Funny.
  • How can you deceive yourself, when you are both the liar and the one lied to? Follow-up: Which of you knows the truth?
  • How much could a person change before friends would be right to call them someone else? Follow-up: Is that a figure of speech or a fact?
  • How much of who a person is was ever chosen by them? Follow-up: Which parts can still be chosen?
  • If a perfect copy of you existed, what would the two of you owe each other? Follow-up: Which of you keeps the house?
  • If you had been born in another century, in what sense would that person have been you? Follow-up: What is the smallest change that would have made someone else?
  • If you swapped bodies with your dog for a day, who answers for what happens to the sofa? Follow-up: Who gets the treat? Funny.
  • What does the word I refer to when you say it inside a dream? Follow-up: Who wakes up?
  • What is a self: a thing, a story or a habit? Follow-up: If a story, who is telling it?
  • What is the I that seems to sit behind your eyes, and would it show up on any scan? Follow-up: If not, where is it?
  • What makes today's you and tomorrow's you one person, and not two very similar people? Follow-up: Why care about tomorrow's, then?
  • What makes you the same person you were at five? Follow-up: What if you remembered nothing from then?
  • What would be left of a person if you took away everything they learned from others? Follow-up: Would what is left be a person?
  • When people say be yourself, which self do they mean? Follow-up: Who picks?
  • Where does your lap go when you stand up? Follow-up: What else exists only while you sit? Funny.
  • Which could you lose and still be you: your memories, your body or your character? Follow-up: Which loss would your friends notice first?

Time and the universe 20

  • A time traveler goes back and stops her own grandparents from ever meeting. Then who made the trip? Follow-up: What does the puzzle show: that the past is fixed, or that such travel is impossible? The grandfather paradox: a science-fiction puzzle; David Lewis's reply dates from 1976.
  • Are the laws of nature rules the universe obeys, or just a summary of what it does? Follow-up: What would breaking one look like?
  • How likely is it that we are alone in the universe, and what would either answer change? Follow-up: Which answer is stranger?
  • If the future already exists, what are we doing when we plan? Follow-up: If it does not, what makes a prediction true?
  • If the whole universe froze for a year and then carried on, what would make it a year? Follow-up: Who could tell?
  • If tomorrow never comes, what have we all been writing in our calendars? Follow-up: What day is it for someone with jet lag? Funny.
  • If you sleep through an hour, where did it go? Follow-up: Do you want it back? Funny.
  • Suppose this life will come round again, the same in every detail, without end. What would make a life worth that? Follow-up: How would knowing it change an ordinary Tuesday? Eternal recurrence: Friedrich Nietzsche, The Gay Science, section 341.
  • What could it mean for the universe to have a beginning, with no before? Follow-up: What would a before have been made of?
  • What does the size of the universe change about how much a human life matters? Follow-up: Would a small universe make us matter more?
  • What is the present, and how long does it last? Follow-up: How much of it is already memory?
  • What is the universe expanding into, and did anyone ask the neighbors? Follow-up: What would the complaint say? Funny.
  • What is time, to someone who has never seen a clock? Follow-up: What would they be missing?
  • What will people in the year 3000 find hardest to believe about us? Follow-up: What will they envy?
  • What would be different if all of space doubled in size overnight, rulers included? Follow-up: If nothing, did anything happen?
  • Where does the past go? Follow-up: In what sense is yesterday still real?
  • Why does time seem to run in one direction only? Follow-up: What would a world running backward look like from inside?
  • Why is there a world at all, when nothing would have been simpler? Follow-up: What kind of answer would even count?
  • Would living forever make a life better or worse? Follow-up: What would people put off?
  • You travel to the very edge of the universe and stretch out your hand. What happens to it? Follow-up: If it goes through, where is the edge now? The edge of the universe: Archytas of Tarentum, as reported by Eudemus.

Society and fairness 22

  • Are humans naturally cooperative or naturally competitive, and what would settle it? Follow-up: Which way do small children lean?
  • Does a country belong more to the people in it now, or to everyone who ever will be? Follow-up: Who speaks for the second group?
  • How can a rule be the same for everyone and still be unfair? Follow-up: What would fix it without creating a new unfairness?
  • How much inequality is fair, if everyone had the same start? Follow-up: And if nobody chose their talents?
  • If a fair process gives a bad result, which should change, the process or the result? Follow-up: Who is trusted to judge the result?
  • Imagine people living with no government, no laws and nobody to settle disputes. How does a typical day go? Follow-up: What is the first rule they would agree on? The state of nature: Thomas Hobbes, Leviathan (1651).
  • Two partners are questioned apart. Each does best by blaming the other, yet both do better if both stay silent. What should each one do? Follow-up: Where does the same trap show up in ordinary life? The prisoner's dilemma: usually credited to Merrill Flood and Melvin Dresher (1950); the prison story is Albert Tucker's.
  • What can a majority not fairly do to a minority, even by voting? Follow-up: Who gets to say so?
  • What do the living owe the people who built what they inherited? Follow-up: How can a debt to the past be paid?
  • What gives anyone the right to tell anyone else what to do? Follow-up: When does that right run out?
  • What is a society for: to keep people safe, to make them free, or to make them good? Follow-up: Which aim is most dangerous in the wrong hands?
  • What is one thing that is legal and wrong, and one that is illegal and right? Follow-up: What does the gap between law and morals tell us?
  • What is the pettiest law a ruler of the world could fairly pass? Follow-up: Who would break it first? Funny.
  • What makes a punishment fit? Follow-up: Is it about the past act or the next one?
  • What makes something yours? Follow-up: Who agreed to that?
  • What would a town lose first if everyone stopped trusting each other? Follow-up: How is trust rebuilt?
  • Which is fairer: all get the same, all get what they need, or all get what they earn? Follow-up: Which one do families use?
  • Who put the person at the front of the line in charge of the line? Follow-up: What are the unwritten laws of a queue? Funny.
  • Why do people cooperate with strangers they will never meet again? Follow-up: What would stop them?
  • Why does everyone in an elevator agree to face the door, and who enforces it? Follow-up: What happens to a rebel? Funny.
  • Why obey a law you had no part in making? Follow-up: What if you think it is wrong?
  • You must design a society without knowing who you will be in it: rich or poor, strong or weak, any talent or none. What rules do you write? Follow-up: Which of today's rules would not survive that test? The veil of ignorance: John Rawls, A Theory of Justice (1971).

How it works

Nobody has to confess anything here. These 150 abstract philosophy questions are about knowledge, minds, choice, fairness and time, not about your own life, and 25 are classic thought experiments with their authors named. Pick a Theme, press Next question and argue.

Read the full guide

Seven themes and two extra pills

The Theme row holds seven: Knowledge and reality (22), Mind and consciousness (22), Free will (20), Right and wrong (22), Identity and the self (22), Time and the universe (20) and Society and fairness (22). Two more pills cut across them: Thought experiments (25) and Funny (23). For human nature questions, try Right and wrong, which asks Are people kind by nature, or taught to be?

Starter, deeper, abstract

Easy (52 cards) is the starter level: no background needed, and most funny cards sit here. Medium (62) goes a step deeper. Hard (36) is the abstract end, where the difficult questions about life live, such as Why is there a world at all, when nothing would have been simpler?

  • Show follow-up on a thought experiment also names who thought of it, from Plato's cave to John Rawls's veil of ignorance.
  • On the trolley card the follow-up swaps the switch for pushing a bystander onto the track. Let the first answer stand before you press it.
  • No card is about religion or party politics. Print, on the end card, gives your theme as slips, up to 120 at a time.

Questions and answers

What are some questions about the mind?

Mind and consciousness holds 22, such as What is the difference between a brain and a mind? and Where is a thought while you are thinking it? Four are thought experiments: Mary's room, the Chinese room, Nagel's bat and Molyneux's problem.

Are there dumb philosophy questions, or hilarious philosophical questions?

Funny holds 23 that sound silly and are not, such as Where does your lap go when you stand up? and If ants had a moral code, what would its first rule be? None is Hard.

Which are the questions to make you question your existence?

Look under Identity and the self and Time and the universe. One asks What makes you the same person you were at five? Another is Derek Parfit's teletransporter, which destroys you and builds an exact copy on Mars.

What are awesome philosophical questions to start with?

Press Thought experiments and Easy. That leaves seven a group can argue with no reading: the trolley, the ring of Gyges, the ship of Theseus, Descartes' dream, Nagel's bat, the edge of the universe and the state of nature.

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