The Daily Dilemma

Philippa Foot, 1967 · named by Judith Jarvis Thomson, 1976, who later moved the choice to a bystander at the switch (1985)

A runaway trolley will kill five people on the track ahead. You can pull a lever to send it down a side track, where it will kill one person instead. Do you pull the lever?

The positions

1. A

   Pull the lever

   Consequentialism

   Utilitarians from Jeremy Bentham and John Stuart Mill onward

   One death is a better outcome than five, and outcomes are what make an act right.

2. B

   Leave it

   Doing versus allowing

   Some deontologists; Judith Jarvis Thomson came to hold that a bystander may not turn the trolley (2008)

   Turning the trolley makes you the one who kills, and you have no right to choose who dies.

Play the trolley problem →

Judith Jarvis Thomson, 1976, varying Foot's case

The same trolley is heading for five people. This time you stand on a bridge above the track beside a very large stranger. Pushing him off would stop the trolley and save the five, but he would die. Do you push?

The positions

1. A

   Push

   Consequentialism

   Act utilitarians

   The arithmetic is the same as at the lever: one death instead of five.

2. B

   Don't push

   Respect for persons

   Kant's formula of humanity; the doctrine of double effect, traced to Aquinas

   Pushing uses a person merely as a means: his death is the very thing that saves the others.

Read about double effect →

Discussed by Judith Jarvis Thomson, 1976

Five patients will die without organ transplants. A healthy visitor in for a check-up is a match for all five. No one would ever find out. Should the surgeon take his organs?

The positions

1. A

   Operate

   Act consequentialism

   Act consequentialism applied strictly

   If only outcomes count and no one ever learns of it, five lives outweigh one.

2. B

   Refuse, on the numbers

   Rule consequentialism

   Rule utilitarians and other indirect consequentialists

   A practice of killing patients would wreck trust in medicine and cost far more lives than it saves.

3. C

   Refuse: it is murder

   Rights and duties

   Deontologists; Philippa Foot's distinction between negative and positive duties (1967)

   The duty not to kill is stronger than the duty to save, and the visitor has a right not to be used.

Read about deontology →

John Harris, 1975

Imagine a society in which, whenever two or more patients need organs, a fair lottery picks one healthy citizen whose organs will save them. Everyone's overall chance of survival goes up. Should we adopt it?

The positions

1. A

   Adopt it

   Consequentialism

   The argument John Harris pressed in “The Survival Lottery” (1975)

   If letting the patients die is no better than killing one person, refusing the lottery simply chooses more deaths.

2. B

   Reject it

   Killing versus letting die

   Defenders of the line between killing and letting die, such as Philippa Foot (1967); Kantian respect for persons

   Killing an innocent person is worse than failing to save one, and no one is a store of spare parts.

Compare the trolley problem →

Echoes real cases: United States v. Holmes, 1842; R v Dudley and Stephens, 1884

A lifeboat built for twelve holds fifteen, and it is starting to sink. If three people go overboard, twelve will live. If no one does, all fifteen may drown. What should happen?

The positions

1. A

   Draw lots

   Fairness

   The prosecution's argument in United States v. Holmes (1842), that lots should have been cast

   If someone must be lost, everyone should have an equal chance, and no one gets to pick the victims.

2. B

   Save the most

   Consequentialism

   Consequentialist reasoning

   Twelve lives saved is better than fifteen lost, and delay may kill everyone.

3. C

   No one may be thrown

   Rights

   The court in R v Dudley and Stephens (1884), which held that necessity is no defence to murder

   Deliberately killing an innocent person stays wrong, even to save others.

Read about duty-based ethics →

Robert Nozick, 1974

A being gets vastly more pleasure from every resource than anyone else does, so much that giving it everything, while others go without, would maximise total happiness. Should it get everything?

The positions

1. A

   Yes, if the sums say so

   Total utilitarianism

   Strict sum-total utilitarianism

   If happiness is all that counts, it counts the same wherever it lands.

2. B

   No

   Separateness of persons

   Robert Nozick, who invented the monster as an objection; John Rawls's charge that utilitarianism ignores the distinction between persons (1971)

   People are not containers for one shared pool of welfare; each life has its own claim.

Read about Robert Nozick →

Derek Parfit, 1984

World A has ten billion people living excellent lives. World Z has vastly more people whose lives are only just worth living, but its total happiness is greater. Is World Z better?

The positions

1. A

   Yes, Z is better

   Total view

   Torbjörn Tännsjö, “Why We Ought to Accept the Repugnant Conclusion” (2002)

   Our recoil may come from failing to picture huge numbers; more lives worth living is more good.

2. B

   No, A is better

   Quality matters

   Derek Parfit, who called the conclusion repugnant and searched for a theory that avoids it

   A world is not improved by trading excellent lives for barely tolerable ones.

Read about utilitarianism →

Peter Singer, 1972

Walking past a shallow pond, you see a child drowning. Wading in will ruin your expensive shoes, and of course you save the child. Are you just as obliged to give that much money to save a stranger's life far away?

The positions

1. A

   Yes, just as obliged

   Impartial consequentialism

   Peter Singer, “Famine, Affluence, and Morality” (1972)

   Distance does not change how much a life matters, and you can prevent the death at modest cost.

2. B

   Good to give, but beyond duty

   Supererogation

   The idea of acts beyond the call of duty, defended by J. O. Urmson, “Saints and Heroes” (1958)

   Morality leaves room for a life of your own; great generosity is admirable rather than owed.

Read about utilitarianism →

Benjamin Constant and Immanuel Kant, 1797

A friend is hiding in your house. A man intent on killing them knocks and asks whether your friend is inside. May you lie to him?

The positions

1. A

   Lie

   Lying can be right

   Benjamin Constant, Kant's critic; consequentialists; Christine Korsgaard, who argues Kant's own theory allows it (1986)

   Truthfulness is not owed to someone who means to use the truth to do evil.

2. B

   Don't lie

   Kant's strict view

   Kant, “On a Supposed Right to Lie from Philanthropy” (1797)

   Lying is wrong in itself; the crime is the murderer's, but a lie makes you answerable for what follows.

Read about the categorical imperative →

J. J. C. Smart, 1956

On a desert island, you promise a dying man to give his fortune to a horse-racing club. No one else knows. Back home, a hospital could use the money to save lives. Do you keep the promise?

The positions

1. A

   Give it to the hospital

   Act utilitarianism

   J. J. C. Smart, who used the case to defend act (“extreme”) utilitarianism in “Extreme and Restricted Utilitarianism” (1956)

   Breaking the promise harms no one, and the money does far more good elsewhere.

2. B

   Keep the promise

   Duty of fidelity

   W. D. Ross, The Right and the Good (1930); deontologists

   A promise creates a duty of its own, not just a forecast of good results.

Compare Kant and Mill →

William Godwin, 1793

A building is on fire and you can save only one person: a great benefactor whose work will help thousands, or your own mother. Whom do you save?

The positions

1. A

   The benefactor

   Impartiality

   William Godwin, Enquiry Concerning Political Justice (1793), whose case this is

   Each person counts equally, so save the life that will do the most good.

2. B

   Your mother

   Partiality

   Bernard Williams (1976), who argued that a man saving his wife needs no further justification, and that looking for one is a thought too many

   Love and loyalty are not failures of morality; someone who calculates here has missed something.

Read about love →

After Thomas Nagel and Bernard Williams, 1976

Two people drive home equally drunk. One gets home safely. The other hits a child who runs into the road. They made the same choice. Are they equally to blame?

The positions

1. A

   Equally to blame

   The control principle

   The Kantian view that a good or bad will is what counts, not luck in the results (Groundwork, 1785)

   We can fairly be judged only for what was within our control.

2. B

   The one who killed is worse

   Moral luck

   Our ordinary practice, which Thomas Nagel and Bernard Williams argued cannot simply be explained away

   What we actually do in the world, not only what we intend, shapes what we must answer for.

Read about free will →

William James, 1891 · later a short story by Ursula K. Le Guin, 1973

Millions could live in lasting happiness on one condition: a single person, far away, must suffer alone forever. Would you accept the bargain?

The positions

1. A

   Accept

   Utilitarian arithmetic

   Classical utilitarian reasoning taken strictly

   The suffering of one is outweighed by the happiness of millions.

2. B

   Refuse

   Against the bargain

   William James, “The Moral Philosopher and the Moral Life” (1891), who said we would find such happiness hideous

   Some arrangements are wrong however good the totals, because of what they do to one person.

Read about utilitarianism →

Plato, Republic, Book II

You find a ring that makes you invisible. You could take anything and go anywhere, and never be caught. Would you still act justly?

The positions

1. A

   Stay just

   Justice is its own reward

   Socrates in Plato's Republic

   Injustice throws the soul into disorder; the just person is better off even when unseen.

2. B

   Use the ring

   Glaucon's challenge

   The view Glaucon sets out to challenge Socrates: people are just only for fear of being caught

   Take away the risk of punishment and the reason for being just goes with it.

Read about virtue ethics →

David Hume, A Treatise of Human Nature, 1739–40

You know every fact about a situation: who will be hurt, how, and how badly. Do those facts alone tell you what you ought to do?

The positions

1. A

   No, a gap remains

   Hume's law

   Hume, who noticed writers sliding from “is” to “ought” without explanation

   No list of facts implies a value unless a value has already been assumed.

2. B

   Yes, sometimes

   Institutional facts

   John Searle, “How to Derive ‘Ought’ from ‘Is’” (1964), using the example of promising

   Saying “I promise” is a plain fact, and it creates an obligation.

3. C

   Yes: facts about flourishing

   Ethical naturalism

   Philippa Foot, Natural Goodness (2001), in the tradition of Aristotle

   What is good for a human being is a fact about the kind of creature we are.

Read about Hume →

Herodotus, Histories 3.38

The Persian king Darius asked Greeks, who burned their dead, what it would take for them to eat their fathers' bodies, and asked the Callatiae, who ate their dead, what it would take for them to burn them. Each was horrified. Is one custom actually right?

The positions

1. A

   Custom is king

   Cultural relativism

   Herodotus, quoting the poet Pindar

   Every people thinks its own ways best, and there is no neutral ground from which to judge.

2. B

   There are moral truths

   Moral realism

   Plato; Kant; moral realists today

   Disagreement about an answer does not show that there is no answer.

3. C

   Shared values, different beliefs

   A common core

   James Rachels, The Elements of Moral Philosophy (1986), discussing this very story

   Both peoples honour their dead; they differ in their beliefs about what honours them.

Read about relativism →

W. D. Ross, 1930

You promised to meet a friend for something trivial. On the way, you come across an accident where you could help the injured, though it means breaking your promise. Nearly everyone agrees you should stop. But why is stopping right?

The positions

1. A

   Relieving distress is the weightier duty

   Prima facie duties

   W. D. Ross, who used this case in The Right and the Good (1930)

   Both duties are real; here helping is, in Ross's phrase, more of a duty, and not because it produces more good.

2. B

   Because it does more good

   Consequentialism

   Consequentialists

   The promise matters only through its effects, and helping the injured matters far more.

Read about duties →

An everyday dilemma

A close friend, delighted, shows you a haircut you find unflattering. It cannot be undone. They ask what you think. What do you say?

The positions

1. A

   Say you love it

   Act consequentialism

   Act-consequentialist reasoning

   A small untruth spares real hurt and harms no one.

2. B

   Tell the truth, kindly

   Truthfulness

   Kant, for whom lying is always wrong; Sissela Bok, Lying (1978), on the hidden costs of white lies

   Even small lies wear away trust, and your friend did ask.

Read about Kant's test →

An everyday dilemma, after Peter Singer and Nel Noddings

You have some money to give away. A person asking for help is right in front of you. A well-evidenced charity far away could do much more good with the same money. Where does it go?

The positions

1. A

   The most effective charity

   Effective altruism

   Peter Singer, The Life You Can Save (2009); William MacAskill, Doing Good Better (2015)

   If the same gift can help far more people, the person you happen to see has no stronger claim.

2. B

   The person in front of you

   Ethics of care

   Nel Noddings, Caring (1984), for whom obligations grow out of real encounters

   Morality begins in relationships, with the particular person who calls on you.

Read about friendship →

After Jeremy Bentham, 1789

A pig can feel pain and fear about as much as a dog can. Is it wrong to raise and kill animals for food when other food is available?

The positions

1. A

   Their suffering counts equally

   Equal consideration

   Jeremy Bentham's question, not whether they can reason but whether they can suffer (1789); Peter Singer, Animal Liberation (1975)

   Equal suffering deserves equal weight, whatever the species.

2. B

   They have rights

   Animal rights

   Tom Regan, The Case for Animal Rights (1983)

   Animals with lives of their own may not be used as mere resources, whatever the benefits.

3. C

   Our duties are indirect

   Indirect duties

   Kant, Lectures on Ethics: cruelty to animals is wrong because it hardens us towards people

   Duties are owed to rational beings; animals matter through what cruelty does to us.

Read about utilitarianism →

An everyday dilemma, after Confucius and Jane English

Your parents made years of sacrifices for you. Now that you are grown, do you owe them your time and care as a debt?

The positions

1. A

   Yes, a deep duty

   Filial piety

   Confucius, Analects: serve parents with reverence, not just by providing for them

   Respect and care for parents are, as the Analects puts it, the root of humaneness.

2. B

   Not a debt, though love asks a lot

   The friendship model

   Jane English, “What Do Grown Children Owe Their Parents?” (1979)

   Parents' sacrifices are not loans; what grown children should do comes from the relationship as it is now.

Read about Confucianism →

After Anthony Downs, 1957

Your vote will almost certainly not decide the election. Do you have a duty to vote anyway?

The positions

1. A

   Not on the numbers

   Rational choice

   Anthony Downs, An Economic Theory of Democracy (1957), which framed the paradox of voting

   The effort of voting outweighs the tiny chance that your vote decides anything.

2. B

   Yes: what if everyone stayed home?

   Civic duty

   Kantian reasoning about universal rules; civic-duty views

   Democracy works only if citizens play their part, and you cannot make yourself the exception.

3. C

   No duty, but vote well if you vote

   The ethics of voting

   Jason Brennan, The Ethics of Voting (2011)

   There are many ways to serve the common good, and voting carelessly can harm it.

Read about political philosophy →

Niccolò Machiavelli, The Prince, 1532

You lead a group of people and cannot be both feared and loved. Which should you choose?

The positions

1. A

   Feared

   Political realism

   Machiavelli, The Prince, chapter 17

   People break the bond of love when it suits them; the fear of punishment holds.

2. B

   Lead by virtue instead

   Rule by example

   Confucius, Analects 2.1 and 2.3

   Lead by example and ritual, and people develop a sense of shame and order themselves.

Read about political philosophy →

John Rawls, A Theory of Justice, 1971

You must choose the rules for a society without knowing who you will be in it: rich or poor, talented or not, of which sex or faith. Which rules do you choose?

The positions

1. A

   Protect the worst-off

   Justice as fairness

   John Rawls: equal basic liberties, and inequalities only where they benefit the least advantaged

   Behind the veil, you would insure yourself against ending up at the bottom.

2. B

   Maximise the average

   Average utilitarianism

   John Harsanyi (1953, 1955), who argued that an impartial chooser would maximise average welfare

   If you are equally likely to be anyone, the best bet is the highest average.

3. C

   Reject the set-up

   Entitlement theory

   Robert Nozick, Anarchy, State, and Utopia (1974)

   Justice depends on how people came to hold what they have, not on a pattern a designer would pick.

Play the veil of ignorance →

Robert Nozick, 1974

Start from whatever share-out of wealth you think is fair. A million fans each freely pay a star player a small sum to watch him play. Now he is far richer than anyone else. Is the new distribution unjust?

The positions

1. A

   No: it came about freely

   Libertarianism

   Robert Nozick: whatever arises by just steps from a just situation is itself just

   Keeping any fixed pattern would mean constantly interfering with people's free choices.

2. B

   It can be

   Egalitarianism

   G. A. Cohen, “Robert Nozick and Wilt Chamberlain: How Patterns Preserve Liberty” (1977); followers of Rawls

   The fans did not agree to the power over others that such wealth brings; patterns can protect liberty too.

Compare Rawls and Nozick →

Hobbes, 1651 · Locke, 1689 · Rousseau, 1755

Imagine there were no government, no police and no laws at all. What would human life be like?

The positions

1. A

   A war of all against all

   Order first

   Thomas Hobbes, Leviathan (1651)

   Without a power to keep everyone in awe, fear and competition make life nasty, brutish and short.

2. B

   Mostly peaceful, but insecure

   Natural rights

   John Locke, Second Treatise of Government (1689)

   Natural rights already exist; government is needed only to judge and enforce them fairly.

3. C

   Innocent, until property arrives

   Natural goodness

   Jean-Jacques Rousseau, Discourse on Inequality (1755)

   Natural humans are simple and compassionate; inequality and vice come with society.

Compare Hobbes and Locke →

Socrates, Thoreau and King

A law you believe is seriously unjust requires you to take part in something. Breaking it carries a penalty. What do you do?

The positions

1. A

   Obey, and argue for change

   Obligation to the law

   Socrates in Plato's Crito, refusing to escape his death sentence

   Having lived under the laws and accepted their benefits, you may try to persuade them but not break them.

2. B

   Refuse to take part

   Conscience first

   Henry David Thoreau, “Resistance to Civil Government” (1849), later known as “Civil Disobedience”

   Your conscience, not the majority, decides what you will lend your hand to.

3. C

   Break it openly and accept the penalty

   Civil disobedience

   Martin Luther King Jr., “Letter from Birmingham Jail” (1963)

   Breaking an unjust law openly, and willingly taking the penalty, shows the highest respect for law.

Read about the social contract →

After John Stuart Mill, 1859

An adult wants to do something dangerous only to themselves, such as riding a motorbike without a helmet. Should the law stop them?

The positions

1. A

   No: their life, their call

   The harm principle

   John Stuart Mill, On Liberty (1859): power may be used against someone's will only to prevent harm to others

   Over their own body and mind, the individual is sovereign.

2. B

   Yes, sometimes

   Paternalism

   Gerald Dworkin, “Paternalism” (1972)

   Some limits protect the very freedom and future choices a person would want to keep.

Read about political philosophy →

William Forster Lloyd, 1833 · Garrett Hardin, 1968

Herders share a common pasture. Each gains by adding one more animal, while the cost of overgrazing is shared by all. Left alone, the pasture will be ruined. What is the fix?

The positions

1. A

   Enforceable limits from outside

   Mutual coercion

   Garrett Hardin, “The Tragedy of the Commons” (1968): mutual coercion, mutually agreed upon, or private ownership

   Appeals to conscience fail; only enforceable rules stop the ruin.

2. B

   Let the users govern it

   Self-governance

   Elinor Ostrom, Governing the Commons (1990)

   Communities around the world have managed shared resources for centuries with rules of their own.

Read about political philosophy →

Mencius, 4th century BCE

Anyone who suddenly saw a small child about to fall into a well would feel alarm and concern. What does that tell us about human nature?

The positions

1. A

   We are naturally good

   Goodness by nature

   Mencius: everyone has sprouts of compassion that need cultivating (Confucianism)

   The alarm comes instantly, before any thought of reward or reputation.

2. B

   We are naturally bad

   Goodness by effort

   Xunzi: human nature is bad, and goodness comes from ritual, teachers and deliberate effort

   Left to ourselves we follow desire; virtue is a craft that must be learned.

3. C

   Neither, by nature

   Nature is neutral

   Gaozi, Mencius's rival, who likened human nature to water that flows whichever way it is channelled

   Nature supplies raw drives; good and bad come from what shapes them.

Read about Confucianism →

Robert Nozick, 1974

A machine can give you any experiences you like: a lifetime of love, achievement and joy, indistinguishable from the real thing. Once inside, you will not know. Do you plug in for life?

The positions

1. A

   Plug in

   Hedonism

   Hedonists: if pleasure is the only thing good in itself, nothing is lost

   What matters in a life is how it feels from the inside.

2. B

   Stay out

   Contact with reality

   Robert Nozick: we want to actually do things and to be a certain kind of person

   A life of simulated achievement is not a life of achievement.

3. C

   It depends where you start

   Status quo bias

   Felipe De Brigard (2010), who found that people told they are already in a machine often choose to stay

   Our refusal may be attachment to the life we have rather than love of reality.

Face the experience machine →

After Jeremy Bentham and John Stuart Mill

A safe pill would make you permanently and simply content, but you would lose all appetite for hard books, difficult art and big questions. Do you take it?

The positions

1. A

   Take it

   Quantity of pleasure

   Jeremy Bentham, for whom a simple game is worth as much as poetry if it gives as much pleasure (1825)

   Pleasure is pleasure; its source adds nothing to its value.

2. B

   Refuse

   Higher pleasures

   John Stuart Mill, Utilitarianism (1861): better to be Socrates dissatisfied than a fool satisfied

   Pleasures of the mind are higher in quality, not just in quantity.

Read about hedonism →

Jean-Paul Sartre, Existentialism Is a Humanism, 1945

During the war, a young man must choose: stay with his mother, who lives only for him, or leave to join the fight against the occupation. What should he do?

The positions

1. A

   Stay with his mother

   Filial duty

   Confucian filial piety; the ethics of care

   A concrete duty to the one person who depends on you outweighs a distant contribution.

2. B

   Join the fight

   The larger cause

   Consequentialist reasoning

   The cause touches countless lives; his mother's need, though real, is one.

3. C

   No theory can decide

   Existentialism

   Sartre: he must choose, and in choosing he makes himself

   No ethical rule settles it; whatever he does, the choice is his to own.

Read about existentialism →

Albert Camus, 1942

Sisyphus is condemned forever to push a boulder up a hill, only to watch it roll back down. Can such a life be meaningful?

The positions

1. A

   Yes, in revolt

   Absurdism

   Camus: one must imagine Sisyphus happy

   Meaning lies in facing the absurd with open eyes and living fully anyway.

2. B

   Yes, if he wants it

   Meaning from within

   Richard Taylor (1970): give Sisyphus a desire to roll stones, and his life is filled with meaning

   Meaning comes from caring about what you do.

3. C

   Not as it stands

   Meaning needs worth

   Susan Wolf (2010): meaning arises when subjective attraction meets objective attractiveness

   Loving a pointless task is not enough; the task must also be worth doing.

Read about absurdism →

Friedrich Nietzsche, The Gay Science, 1882

A demon tells you that you will live this exact life again, every moment of it, endlessly. Is that the best news you could hear, or the worst?

The positions

1. A

   The best

   Love of fate

   Nietzsche's ideal of affirming life; Epictetus's advice to want things to happen as they do

   To want your life again is to love it, pains included.

2. B

   The worst

   Pessimism

   Arthur Schopenhauer, for whom life's suffering outweighs its goods

   A life judged honestly is not one anyone should wish to repeat.

Read about Nietzsche →

Epicurus, Letter to Menoeceus, c. 300 BCE

When you are dead, you will not exist to experience anything, including being dead. Is death bad for the person who dies?

The positions

1. A

   No

   Epicureanism

   Epicurus: where death is, I am not; Lucretius: we do not mourn the time before we were born

   What is never experienced cannot harm you.

2. B

   Yes

   The deprivation account

   Thomas Nagel, “Death” (1970)

   Death is bad because of the goods of life it takes away, even if no one feels the loss.

Read: is death bad? →

Bernard Williams, 1973, after Karel Čapek's play The Makropulos Affair

You are offered an elixir: you would never age or die, though you could stop taking it whenever you liked. Do you drink?

The positions

1. A

   Drink

   Immortality can be good

   John Martin Fischer, “Why Immortality Is Not So Bad” (1994): some pleasures are endlessly repeatable

   A rich mix of renewing goods could keep an endless life worth living.

2. B

   Refuse

   The tedium of immortality

   Bernard Williams, “The Makropulos Case” (1973)

   An endless life would end in boredom, or else you would change so much it would no longer be you.

Read: is immortality desirable? →

Plato, Euthyphro

Is something good because God commands it, or does God command it because it is good?

The positions

1. A

   Good because commanded

   Divine command theory

   William of Ockham, who held that God could have commanded otherwise

   Nothing stands above God's will to make things good or bad.

2. B

   Commanded because good

   Independent goodness

   The horn Socrates presses in the dialogue; Leibniz, Discourse on Metaphysics (1686)

   Otherwise morality would be arbitrary, and calling God good would be empty praise.

3. C

   Goodness is God's own nature

   A third way

   Aquinas; Robert Adams's modified divine command theory; William Alston (1990)

   God commands what is good because God's character is itself the standard of goodness.

Read: does God exist? →

Blaise Pascal, Pensées, published 1670

You cannot prove that God exists or that God does not. If God exists, belief gains you infinitely much; if not, you lose little. Should you bet on God?

The positions

1. A

   Bet on God

   The wager

   Blaise Pascal

   With an infinite prize and a finite stake, wagering on God is the rational choice.

2. B

   Which god?

   The many-gods objection

   Denis Diderot (1746), who noted that an imam could reason in just the same way

   The wager works equally well for rival gods, so it cannot tell you where to bet.

3. C

   Not without evidence

   Evidentialism

   W. K. Clifford, “The Ethics of Belief” (1877)

   It is wrong to believe anything on insufficient evidence, whatever the payoff.

Read: does God exist? →

An ancient problem, pressed in Hume's Dialogues, 1779

If God is all-powerful and wholly good, why is there so much suffering, including suffering that no one deserves?

The positions

1. A

   Free will

   The free will defence

   Augustine; Alvin Plantinga (1974)

   A world of free creatures is better than one without them, and freedom includes the power to do evil.

2. B

   Soul-making

   Irenaean theodicy

   John Hick, Evil and the God of Love (1966), drawing on Irenaeus

   Courage, compassion and character can only grow in a world with real hardship.

3. C

   It counts against God

   The evidential argument

   William Rowe (1979), with his case of a fawn dying slowly in a forest fire

   Some suffering seems to serve no greater good at all.

Read about the problem of evil →

Frank Jackson, 1982

Mary is a brilliant scientist who knows every physical fact about colour vision, but she has lived all her life in a black-and-white room. One day she walks out and sees a red rose. Does she learn something new?

The positions

1. A

   Yes, a new fact

   Anti-physicalism

   Frank Jackson's original knowledge argument (1982), which he later gave up

   If she learns something, the physical facts were not all the facts.

2. B

   No, a new ability

   The ability hypothesis

   David Lewis (1983, 1988) and Laurence Nemirow

   She gains the ability to recognise and imagine red, not new information.

3. C

   An old fact, known in a new way

   Phenomenal concepts

   Brian Loar (1990) and others

   She meets a fact she already knew, now under a new, experiential concept.

Enter Mary's room →

Robert Kirk, 1974 · David Chalmers, 1996

Could there be a being exactly like you, atom for atom, that behaves just as you do, but has no inner experience at all?

The positions

1. A

   Yes, so mind is not just matter

   Property dualism

   David Chalmers, The Conscious Mind (1996)

   If such a zombie is conceivable, consciousness is something over and above the physical.

2. B

   No, it is not really conceivable

   Physicalism

   Daniel Dennett

   We underestimate what we are imagining; a perfect physical duplicate would be conscious.

3. C

   Conceivable, but not possible

   Type-B physicalism

   Brian Loar; Christopher Hill and Brian McLaughlin (1999)

   What we can imagine tells us about our concepts, not about what could really exist.

Read about philosophical zombies →

John Searle, 1980

You sit in a room with a rulebook for answering written Chinese questions with Chinese symbols. You do not understand a word, but your answers are flawless. Does anything in the room understand Chinese?

The positions

1. A

   No

   Biological naturalism

   John Searle: manipulating symbols is not enough for meaning

   Running the right program is not the same thing as understanding.

2. B

   The whole system does

   The systems reply

   Ned Block, Daniel Dennett, Douglas Hofstadter and others

   You are one part of a system, and understanding belongs to the whole.

3. C

   Not yet: give it a body

   The robot reply

   Margaret Boden, Stevan Harnad and others

   Connect the symbols to sensors and actions in the world, and meaning can follow.

Enter the Chinese room →

Alan Turing, 1950

After a long conversation by text, you cannot tell whether you have been talking to a person or a machine. Should you say the machine thinks?

The positions

1. A

   Yes

   Behavioural test

   Alan Turing, “Computing Machinery and Intelligence” (1950), who proposed replacing “Can machines think?” with this test

   We judge other people's minds by how they behave; the same standard should apply.

2. B

   No, behaviour is not enough

   Inner workings matter

   Ned Block (1981), whose giant lookup table could pass without thinking; John Searle (1980)

   How a system produces its answers matters, not just the answers.

Read: can machines think? →

Zenon Pylyshyn, 1980 · John Searle, 1992 · David Chalmers, 1995

One by one, your neurons are replaced by chips that do exactly the same job. You go on talking and acting just as before. When the last neuron is gone, are you still conscious?

The positions

1. A

   Yes, throughout

   Organisational invariance

   David Chalmers's fading qualia argument: the same functional organisation gives the same experience

   It is absurd that experience could fade while you go on sincerely saying everything is fine.

2. B

   Not necessarily

   Biological naturalism

   John Searle, The Rediscovery of the Mind (1992): your consciousness might shrink while your behaviour stays the same

   Consciousness is caused by particular biology, not by organisation alone.

Read about machine consciousness →

Thomas Nagel, 1974

Bats find their way by echolocation. Could any amount of science tell you what it is like to be a bat?

The positions

1. A

   No

   The subjective point of view

   Thomas Nagel, “What Is It Like to Be a Bat?” (1974)

   Experience has a point of view that objective description leaves out.

2. B

   Yes, in principle

   Physicalism

   Physicalists such as Daniel Dennett, who doubt that anything is left over

   Know enough about how the bat's brain works and nothing further remains to be known.

Read about consciousness →

John Locke, An Essay Concerning Human Understanding, 1689

Could the colour you see when you look at grass be the colour I see when I look at a ripe tomato, without either of us ever being able to tell?

The positions

1. A

   Yes, possibly

   Private qualities

   John Locke, who raised the possibility

   We learn colour words from the same objects, so a hidden swap would never show.

2. B

   The question is confused

   No private essence

   Ludwig Wittgenstein's beetle in a box (1953); Daniel Dennett, “Quining Qualia” (1988)

   A private inner quality that could make no difference to anything drops out of the picture.

Read about qualia →

Donald Davidson, 1987

Lightning strikes a dead tree in a swamp and, by sheer chance, creates a molecule-for-molecule duplicate of you. It walks to your home and greets your friends by name. Does it have thoughts about them?

The positions

1. A

   Yes, the same as yours

   Internalism

   Internalists, for whom the mind is settled by what is inside the head

   Same brain, same thoughts.

2. B

   No, not at first

   Externalism

   Donald Davidson, “Knowing One's Own Mind” (1987)

   Thoughts get their content from causal history, and Swampman has none.

Read about philosophy of mind →

Hilary Putnam, 1975

On Twin Earth everything is as it is here, except that the clear liquid in its rivers is not H₂O but a different chemical, XYZ. When your twin says “water”, do they mean what you mean?

The positions

1. A

   No

   Semantic externalism

   Hilary Putnam, “The Meaning of ‘Meaning’” (1975): meanings are not just in the head

   Their word picks out XYZ and yours picks out H₂O, even with identical thoughts inside.

2. B

   Yes, in one sense

   Narrow content

   Jerry Fodor, Psychosemantics (1987)

   What the twins share inside their heads is a real kind of meaning, and it explains their behaviour.

Read about philosophy of mind →

Plutarch, Life of Theseus · the rebuilt-ship twist from Thomas Hobbes, 1655

Over the years, every plank of a famous ship is replaced. Someone collects the old planks and rebuilds the original ship from them. Which one is the ship of Theseus?

The positions

1. A

   The repaired ship

   Continuity

   Views on which identity follows gradual, unbroken change

   It never stopped sailing; it changed bit by bit, as we all do.

2. B

   The rebuilt ship

   Same matter

   The view that an object is its original material

   Every original plank is back, in its original place.

3. C

   No fact of the matter

   A verbal question

   Hume, for whom such questions of identity are grammatical rather than philosophical

   Once the facts are laid out, all that is left is how we choose to use a word.

Rebuild the ship →

Derek Parfit, Reasons and Persons, 1984

A teleporter scans your body, destroys it, and builds an exact copy on Mars, memories and personality included. The copy wakes up feeling just like you. Would you step in?

The positions

1. A

   Step in

   Psychological continuity

   Derek Parfit: what matters is psychological connection and continuity, not the same body

   Everything you care about in being yourself arrives on Mars.

2. B

   Refuse

   Animalism

   Eric Olson, The Human Animal (1997): you are a living organism, and the organism is destroyed

   The person on Mars is a perfect copy, and you are dead.

Read about personal identity →

David Wiggins, 1967 · developed by Derek Parfit, 1971 and 1984

Your brain is split in two and each half is transplanted into a new body. Both people wake up with your memories and character. Which one is you?

The positions

1. A

   Neither, and that is fine

   Identity is not what matters

   Derek Parfit: you get everything that matters in survival, twice over

   Surviving as two people is no worse than ordinary survival.

2. B

   There were two of you all along

   Overlapping persons

   David Lewis, “Survival and Identity” (1976)

   Two persons shared one body until the split, and each carries on.

3. C

   One of them, but we cannot tell which

   A further fact

   Richard Swinburne (1984): personal identity is a further fact, such as a soul

   Who you are is not settled by memories or matter, so there is an answer we cannot see.

Read about personal identity →

John Locke, Essay, 2nd edition, 1694

Suppose the soul of a prince, carrying the memories of the prince's life, enters the body of a cobbler as soon as the cobbler's own soul has left it. Who is the prince now?

The positions

1. A

   The one with the prince's memories

   Consciousness

   John Locke: personal identity reaches as far as consciousness does

   Being the same person means being the same continuing consciousness.

2. B

   The one with the prince's body

   Animalism

   Animalists such as Eric Olson: you are a human animal

   The animal that was born and grew up is still there, now with different memories.

Read about personal identity →

The Questions of King Milinda (Milindapañha)

Is a chariot its wheels? Its axle? Its frame? None of these alone, and nothing extra besides. Ask the same about yourself: is there a self beyond your body, feelings, perceptions and thoughts?

The positions

1. A

   No: “I” is a convenient name

   No-self

   The monk Nāgasena and the Buddhist teaching of no-self; Hume's bundle of perceptions

   Look for the self and you find only changing parts and processes.

2. B

   Yes: a true self underneath

   Ātman

   The Upanishads and Advaita Vedānta (Hindu philosophy)

   Behind changing experience stands a witness that does not change.

3. C

   Yes: a thinking soul

   Substance dualism

   Descartes: I am a thinking thing, distinct from the body

   The one who thinks and doubts cannot be a mere heap of parts.

Read about Buddhism →

René Descartes, 1637 and 1641

Doubt everything you can: your senses, your memories, even mathematics. Is there anything left that you cannot doubt?

The positions

1. A

   That I exist

   Rationalism

   Descartes: I think, therefore I am

   Even doubting is thinking, and thinking needs a thinker.

2. B

   Only that there are thoughts

   The bundle view

   Hume: looking inward, I never catch a self, only perceptions

   The “I” is an extra assumption; all you meet are passing experiences.

3. C

   Nothing at all

   Pyrrhonism

   Sextus Empiricus and the ancient Pyrrhonian sceptics

   Even that would be a claim; the sceptic suspends judgement on everything.

Read about the cogito →

Hilary Putnam, 1981 (the vat image goes back to Gilbert Harman, 1973), updating Descartes's evil demon

Suppose a scientist had removed your brain and wired it to a computer that feeds it exactly the experiences you are having now. Can you know that this is not happening?

The positions

1. A

   No, you cannot rule it out

   Radical scepticism

   The sceptical argument Descartes built in his First Meditation (1641) with an evil demon

   Any evidence you could point to would be part of the simulation.

2. B

   Yes: I know I have hands

   Common sense

   G. E. Moore, “Proof of an External World” (1939)

   I am more sure that I have hands than I am of any premise in a sceptical argument.

3. C

   The scenario defeats itself

   Semantic externalism

   Hilary Putnam, Reason, Truth and History (1981)

   A brain in a vat's word “vat” would not refer to real vats, so it could not truly say it was one.

Read about scepticism →

Zhuangzi, chapter 2, 4th century BCE

Zhuangzi dreamed he was a butterfly, flitting happily about, with no idea he was Zhuangzi. Then he woke, and could not tell whether he was a man who had dreamed of being a butterfly, or a butterfly now dreaming of being a man. Can you be sure you are awake?

The positions

1. A

   Yes

   Coherence

   Descartes in his Sixth Meditation: waking life is linked by memory in a way dreams are not

   Dreams do not join up with the rest of your life; waking experience does.

2. B

   No, not for certain

   Dream scepticism

   Descartes's dream argument in the First Meditation; the ancient sceptics

   There are no sure signs that tell waking from dreaming.

3. C

   The question dissolves

   The transformation of things

   Zhuangzi, who ends the story by calling it the transformation of things (Daoism)

   Perspectives shift into one another; no single standpoint gets to settle which one is real.

Read about Daoism →

William Molyneux, in a letter to John Locke, 1688

A person born blind has learned to tell a cube from a sphere by touch. Their sight is restored. Seeing the two shapes for the first time, without touching them, can they tell which is which?

The positions

1. A

   No

   Empiricism

   Molyneux himself, John Locke and George Berkeley

   The links between sight and touch must be learned from experience.

2. B

   Yes

   Rationalism

   Gottfried Wilhelm Leibniz (1704), given time to reason it out

   The geometry is the same, and reason can connect what the two senses deliver.

A 2011 study (Held and colleagues) found that newly sighted patients could not match the shapes at first, but the three who were retested a few days later could.

Compare rationalism and empiricism →

David Hume, 1748 · Bertrand Russell's chicken, 1912

Every morning of its life, the farmer has fed the chicken, and it expects to be fed tomorrow. One day the farmer wrings its neck instead. Was the chicken's expectation rational, and is ours that the sun will rise tomorrow?

The positions

1. A

   Not justified, just habit

   Humean scepticism

   Hume: no argument shows that the future will resemble the past

   We expect it out of custom, and we cannot help doing so.

2. B

   Science does not need induction

   Falsificationism

   Karl Popper: theories are bold guesses, tested by trying to refute them

   We never prove a law true; we keep it until it fails.

3. C

   Justified as the best bet

   Pragmatic vindication

   Hans Reichenbach, Experience and Prediction (1938)

   If any method of prediction works, induction will.

Read about the problem of induction →

Bertrand Russell, 1948 · Edmund Gettier, 1963

You glance at a clock that reads two o'clock, and you believe it is two. It is, but the clock stopped exactly twelve hours ago. Did you know the time?

The positions

1. A

   No, I was lucky

   Knowledge excludes luck

   Russell, who used the case to show that true belief is not enough; most epistemologists since Gettier (1963)

   A belief that is true by accident is not knowledge.

2. B

   Yes

   Knowledge as true belief

   Crispin Sartwell, “Why Knowledge Is Merely True Belief” (1992)

   Knowledge is just true belief; justification is how we get there, not part of what it is.

Read about knowledge →

Karl Popper, Conjectures and Refutations, 1963

A theory can explain any outcome at all: whatever happens, it has a story for why. Is that a strength or a weakness?

The positions

1. A

   A weakness

   Falsifiability

   Karl Popper: a theory that no possible observation could refute is not scientific

   A theory earns credit by risking being wrong.

2. B

   Not necessarily

   Paradigms

   Thomas Kuhn, The Structure of Scientific Revolutions (1962)

   Working science routinely shields its central theory from awkward results, and that is often how progress happens.

3. C

   Judge the whole research programme

   Research programmes

   Imre Lakatos (1970)

   Adjustments are fine as long as the programme keeps predicting new facts.

Read about falsifiability →

Plato and Aristotle, 4th century BCE

No circle anyone has drawn is perfect, yet we know exactly what a perfect circle is. Does the perfect circle exist, and if so, where?

The positions

1. A

   Yes, more truly than any drawing

   Platonism

   Plato's theory of Forms

   Unchanging Forms are what make imperfect copies recognisable at all.

2. B

   Only in round things

   Moderate realism

   Aristotle: forms exist in particular things, not apart from them

   Circularity is real, but only as the shape of actual things.

3. C

   Only as a word or idea

   Nominalism

   William of Ockham

   Only particular things exist; “circle” is a general sign we apply to many of them.

Compare Plato and Aristotle →

George Berkeley, 1710

When everyone leaves a room, does the furniture go on existing?

The positions

1. A

   Of course

   Realism

   G. E. Moore, “The Refutation of Idealism” (1903); common-sense realism

   Things exist whether or not anyone perceives them.

2. B

   Only as perceived, by God

   Idealism

   George Berkeley: to be is to be perceived

   Objects are collections of ideas, and God's perception keeps them in being.

3. C

   We cannot know things in themselves

   Transcendental idealism

   Kant, Critique of Pure Reason (1781)

   We know things only as they appear through the forms of our experience.

Read about idealism →

Prior, Broad and Putnam

Your tenth birthday happened. Does it still exist, in any sense, or is only the present real?

The positions

1. A

   Only the present exists

   Presentism

   Arthur Prior

   The past was and the future will be, but only the present is.

2. B

   All times are equally real

   Eternalism

   Hilary Putnam, “Time and Physical Geometry” (1967), drawing on relativity

   Relativity leaves no universal “now”, so past, present and future exist alike.

3. C

   The past is real, the future is not yet

   The growing block

   C. D. Broad, Scientific Thought (1923)

   Reality grows as new moments are added, and the past stays fixed.

Read: does time exist? →

Eubulides of Miletus, 4th century BCE

A million grains of sand make a heap. Take one away and it is still a heap. Keep going. Is there a single grain whose removal turns a heap into a non-heap?

The positions

1. A

   Yes, but we cannot know which

   Epistemicism

   Timothy Williamson, Vagueness (1994)

   Classical logic holds, and vagueness is a limit on what we can know.

2. B

   Somewhere, but at no particular grain

   Supervaluationism

   Kit Fine (1975)

   There are many acceptable sharp cut-offs, and no fact picks between them.

3. C

   It fades by degrees

   Degrees of truth

   Fuzzy-logic approaches

   “This is a heap” becomes gradually less true, grain by grain.

Read about famous paradoxes →

Eubulides of Miletus, 4th century BCE

Consider the sentence: “This sentence is false.” Is it true or false?

The positions

1. A

   Neither

   Truth-value gaps

   Saul Kripke, “Outline of a Theory of Truth” (1975)

   The sentence never receives a truth value, because nothing grounds it.

2. B

   Both

   Dialetheism

   Graham Priest

   Some contradictions are true, and logic can be built to cope with them.

3. C

   It is not a proper sentence

   A hierarchy of languages

   Alfred Tarski (1933)

   A language cannot consistently define its own truth; that takes a higher language.

Read about famous paradoxes →

Zeno of Elea, 5th century BCE, as reported by Aristotle

Achilles races a tortoise that has a head start. By the time he reaches where it was, it has moved on a little. By the time he reaches that point, it has moved again, and so on forever. Can Achilles ever overtake it?

The positions

1. A

   No: motion is an illusion

   Eleatic monism

   Zeno, defending Parmenides

   If the argument is sound, reality is one and change is only appearance.

2. B

   Yes: an infinite series can have a finite sum

   Modern mathematics

   The mathematics of limits, made rigorous in the 19th century

   Infinitely many shrinking steps add up to a finite distance and a finite time.

3. C

   Yes: the infinity is only potential

   Potential infinity

   Aristotle, Physics

   A distance can be divided without end, but it is not made of infinitely many actual parts.

Read about famous paradoxes →

Devised by the physicist William Newcomb · published by Robert Nozick, 1969

A predictor that is almost never wrong sets two boxes before you. Box A holds a thousand. Box B holds a million if it predicted you would take only B, and nothing if it predicted you would take both. The boxes are already filled. One box or both?

The positions

1. A

   Only box B

   Evidential decision theory

   Evidential decision theory, the approach of Richard Jeffrey's The Logic of Decision (1965)

   People who take one box almost always walk away with a million.

2. B

   Both boxes

   Causal decision theory

   Causal decision theorists, such as David Lewis, “Why Ain'cha Rich?” (1981)

   The money is already there or it is not; taking both cannot leave you worse off.

Read about Robert Nozick →

Arnold Zuboff, 1980s · Piccione and Rubinstein, 1997 · made famous by Adam Elga, 2000

Beauty is put to sleep and a fair coin is tossed. If heads, she is woken once. If tails, she is woken twice, and her memory of the first waking is erased. Each time she wakes, she is asked how likely it is that the coin landed heads. What should she say?

The positions

1. A

   One half

   Halfers

   David Lewis, “Sleeping Beauty: Reply to Elga” (2001)

   On waking she learns nothing she did not know when the coin was tossed.

2. B

   One third

   Thirders

   Adam Elga, “Self-Locating Belief and the Sleeping Beauty Problem” (2000)

   Of all the wakings that happen, only one in three follows heads.

Read about famous paradoxes →

Merrill Flood and Melvin Dresher, 1950 · the prison story by Albert Tucker

You and a partner are questioned separately. If you both stay silent, you each get one year. If one betrays the other, the betrayer walks free and the other gets ten. If both betray, both get five. What do you do?

The positions

1. A

   Betray

   Game theory

   Standard game theory, in which betrayal is the dominant strategy

   Whatever your partner does, you do better by betraying.

2. B

   Stay silent

   Cooperation

   Kantian reasoning: act only as you could will everyone to act

   If both of you reason this way, both of you do far better.

3. C

   Depends whether we meet again

   Reciprocity

   Robert Axelrod, The Evolution of Cooperation (1984), whose tournaments were won by Anatol Rapoport's tit for tat

   In repeated games, cooperate first, then do whatever the other player did last.

Read about the social contract →

Pierre-Simon Laplace, 1814

An intellect that knew the position of every particle and every law of nature could predict everything you will ever do. If such a demon could exist, are your choices free?

The positions

1. A

   Yes, free in the way that matters

   Compatibilism

   Hume; Harry Frankfurt; Daniel Dennett

   Freedom means acting from your own reasons and desires, not escaping cause and effect.

2. B

   No, freedom is an illusion

   Hard determinism

   Baruch Spinoza; Baron d'Holbach

   We feel free only because we do not see the causes of our choices.

3. C

   No demon could predict a free choice

   Libertarianism

   Thomas Reid; Robert Kane

   Free agents are real causes, and what they will do is not fixed in advance.

Read about free will →

Harry Frankfurt, 1969

Jones decides to do something wrong. Unknown to him, a neuroscientist was ready to force that same decision if he had wavered, but never needed to step in. Jones could not have done otherwise. Is he responsible?

The positions

1. A

   Yes

   Responsibility without alternatives

   Harry Frankfurt, “Alternate Possibilities and Moral Responsibility” (1969)

   What matters is why he acted, not whether he could have acted differently.

2. B

   No, or the case is rigged

   Alternatives matter

   David Widerker (1995) and other libertarians

   Either the device settles his choice in advance, or he had an alternative after all.

Read about compatibilism →

Plato, Hume, Kant and Santayana

Two people disagree about whether a painting is beautiful. Is one of them right?

The positions

1. A

   No, beauty is in the beholder

   Subjectivism

   George Santayana, The Sense of Beauty (1896): beauty is pleasure regarded as a quality of the thing

   Calling something beautiful reports how it makes us feel.

2. B

   Yes, the best judges agree

   A standard of taste

   Hume, “Of the Standard of Taste” (1757)

   Taste varies, but practised, unprejudiced critics converge, and their joint verdict is the standard.

3. C

   We judge as if everyone should agree

   Subjective universality

   Kant, Critique of Judgment (1790)

   A judgement of beauty rests on feeling, yet it claims everyone's agreement.

4. D

   Yes, beauty is real

   Platonism

   Plato, Symposium

   Beautiful things share in a Beauty that exists in itself.

Read: what is beauty? →

Danto, 1964 · Dickie, 1974 · Tolstoy, 1897

An artist takes an ordinary manufactured object, changes nothing, signs it and shows it in a gallery. Is it art?

The positions

1. A

   Yes, if the art world treats it as art

   Institutional theory

   George Dickie, Art and the Aesthetic (1974), developing Arthur Danto's idea of the “artworld” in “The Artworld” (1964)

   What makes something art is its place in a world of theory, galleries and practice.

2. B

   Only if it passes on a feeling

   Expression theory

   Leo Tolstoy, What Is Art? (1897)

   Art is the passing of felt experience from artist to audience.

Read: what is art? →