Week 7 · Chapter

Chapter 7 — Personal Identity and Free Will

Introduction to Philosophy Free sample edition

The module's primary reading · ~45–55 minutes · Objective 4 (compare positions on the mind-body problem, personal identity, and free will, and evaluate them with the thought experiments that test them), with Objective 2 (identify arguments, put them in standard form, judge whether they are valid, sound, or inductively strong, and test claims with counterexamples and thought experiments) carried forward · Read it first this week; the lecture, the slide deck, the tutorial, the quiz, and the Philosophy Workshop all build on it.

In plain language

This week asks two questions about you: what makes you the same person you were years ago, and are your choices free (up to you in the way that praise and blame seem to need) if every choice has causes? You meet a famous puzzle about a ship, a theory that ties a person to their memories, and a Buddhist teaching that there is no permanent self (a self that stays fixed while everything else changes). Then come three answers to the free will question and a 1969 paper by Harry Frankfurt. Your goal is to state each view fairly, not to pick a winner.

Why you already care about this

A band has been playing for years. One by one, the original singer, drummer, guitarist, and bassist have left, and new players have taken their places. By now, not one founding member is on stage. Fans still buy tickets to see "the same band", and the posters still carry the old name. Is it the same band?

Now turn the question on yourself. Find a photo of yourself at five years old. That child had a different body, different tastes, and almost none of your memories. You still say "that's me". What makes it you?

Here is a second puzzle. Think of the last real decision you made: what to eat, what to study, whether to text someone back. It felt open. You could have gone either way. But your choice also had causes: your hunger, your mood, your past, the way your brain works. If every choice has causes, was any of yours free? In 1969 the philosopher Harry Frankfurt published a paper arguing that this question is less simple than it looks, because a person may be responsible even when they could not have done otherwise.

By the end of this chapter you will be able to:

tell numerical identity from qualitative identity, and say which one identity over time asks about;
state both answers to the ship of Theseus in their strongest form, and quote the pinned line with its translator;
state Locke's memory theory, give its strongest objection, and give the reply;
explain the Buddhist teaching of no-self in its own terms, and say why it does not deny that anything exists;
tell determinism from fatalism;
state hard determinism, libertarianism, and compatibilism, each with its strongest objection and a reply;
put Dataset B's argument 4 in standard form, key it for validity only, and say which premise each position rejects;
describe a Frankfurt case and say which principle it challenges.

Carry this sentence with you: the same thing, not the same stuff; caused, not forced.

Where we are

Already covered: Week 1, What Philosophy Is: Socrates and the Examined Life, gave you the counterexample test. Week 2, Arguments and Thought Experiments, gave you standard form, validity, and disjunctive syllogism. Week 3, Plato: Reality and the Forms, asked how appearance differs from reality. Week 4, Knowledge I: Doubt, Reason, and Experience, introduced John Locke as an empiricist. Week 5, Knowledge II: What Knowledge Is, tested a definition with one case. Week 6, The Mind-Body Problem, asked what a mind is.
This week: identity over time; the ship of Theseus; Locke's memory theory; the Buddhist teaching of no-self; determinism and fatalism; hard determinism, libertarianism, and compatibilism; Frankfurt's cases; and what a self must be for responsibility to make sense.
How they connect: Week 6 asked what a mind is at one moment. This week asks what keeps a mind, or a person, the same across time, and whether that person's choices are free. It closes the unit on mind and self.
Where we're going next: Week 8, Midterm Review & Exam, reviews Weeks 1 to 7 by the one distinction each topic asks for, including determinism versus fatalism, and adds one new topic, Pascal's wager.

Two tools from earlier weeks do the heavy lifting. From Week 2, you need standard form: premises numbered P1 and P2, the conclusion last, marked C and introduced by "So". You need valid (the conclusion cannot be false if the premises are true). You also need one form. Disjunctive syllogism is valid: P or Q; not P; so Q. From Week 5, you need the habit of testing a general claim with one well-chosen case.

1. Test the word "same": two senses

Picture two new phones from one box at a store. They have the same model, the same color, and the same scratch-free glass. In one sense they are "the same". In another sense they are plainly two phones: drop one, and the other is fine.

Philosophers give those two senses two names.

Numerical identity — being one and the same thing, so that a thing at one time and a thing at a later time are numerically identical only if they are one thing, not two.
Qualitative identity — being exactly alike in every quality, as two new phones from one box can be, while still being two separate things.

Now think about your own phone after two years. It has a cracked corner, a new battery, and a different case. It is not qualitatively identical to the phone you bought. Yet it seems numerically identical to it: one phone, changed. That is the puzzle of this week in miniature.

Identity over time — the question of whether a thing at an earlier time is numerically the same thing as a thing at a later time, after it has changed.

Worked example — sorting the two senses. Ask which sense of "same" each sentence uses.

"My sister and I wore the same dress to the party." Two dresses, exactly alike: qualitative identity.
"This is the same jacket I wore in high school." One jacket, now older: numerical identity over time.
"The band on stage is the same band I saw years ago." One band, many changes: numerical identity over time, and the hard case.

In words: identity over time is always a question about numerical identity, and change in qualities is what makes it hard.

Misconception check — "changed" does not mean "a different thing". Students often think that if something has changed at all, it cannot be the same thing. It is tempting because we use "not the same" for both senses. The cure is the phone. It is not qualitatively the same after two years, but it is still one phone. Change in qualities does not by itself settle numerical identity.

2. Test a ship: the ship of Theseus

Now the week's thought experiment, the Week 7 case on the course's thought-experiment roster.

Plutarch's Life of Theseus reports that the Athenians preserved Theseus' ship for a very long time. In John Dryden's translation, they kept it sound, for "they took away the old planks as they decayed, putting in new and stronger timber in their place" (Plutarch, Life of Theseus, trans. John Dryden; Dataset C, Q3). Those English words are Dryden's, a translator's, not Plutarch's own. The ship became a standing example among philosophers.

The ship of Theseus — the case, from Plutarch's Life of Theseus, of a ship kept for generations by replacing its old planks with new timber, used to ask whether a thing whose parts are all replaced is still the same thing.

The roster gives the case a question: Is a thing whose parts are all replaced still the same thing? It tests identity over time and the self. Both answers have defenders, so state each one at its strongest.

Worked example — the two answers, each at its strongest. Give each answer, its strongest objection, and a reply from its own side.

The "same ship" answer. The ship was repaired a little at a time. It kept its shape and its job, and at no single step did a new ship begin. So it is the same ship. Strongest objection: by the end, not one plank of the ship Theseus sailed is left. Reply, from the "same ship" side: things that grow and heal, such as a tree or a person, keep their identity while their matter changes. So changed matter alone does not end identity.
The "new ship" answer. A ship is its timber. When every plank is new, the ship is new. Strongest objection: no single plank swap makes a new ship, so this answer must say where the old ship ended, and any line seems arbitrary. Reply, from the "new ship" side: some changes come in degrees, and a vague boundary is still a boundary, the way there is no exact second when day becomes night.

Now a variation, written for this course and not Plutarch's own. Suppose someone saved every old plank as it came off and later built a second ship from them. Now 2 ships each have a claim to be Theseus' ship. The repaired one has the continuity: it was never out of service. The rebuilt one has the original timber. The course keys no answer to which one, if either, is his. The puzzle stays open.

In one plain sentence: the ship of Theseus asks whether a thing survives the replacement of all its parts, and your answer depends on whether a thing is its form and history or its matter.

Misconception check — the quotation is not Plutarch's English. Students often write that Plutarch said the Athenians "took away the old planks as they decayed". It is tempting because the quotation sits next to his name. The cure is the course's rule for translations. The English words are John Dryden's, the translator's. Quote the line with "trans. John Dryden" every time.

3. Turn to persons: Locke's memory theory

The band and the ship are things. The same question about a person is more personal, and it has a name.

Personal identity — the question of what makes a person at one time the same person as someone at an earlier time.

Go back to your five-year-old photo. Your body has grown and changed. Most of the matter in it is not the matter of that child. Yet you seem to be one person who has lasted. What links you?

John Locke, the empiricist you met in Week 4, gave an answer that points to the mind rather than the body. Here it is in the course's words.

Memory theory — John Locke's theory of personal identity, which holds that a person at one time is the same person as someone at an earlier time if they can remember that person's experiences.

Here is the view in its strongest form, through a variation written for this course. Suppose that, by some future science, all your memories were moved into another body, and your old body woke up with none of them. The person with your memories would remember your childhood, your friends, and your last decision. Many people feel sure that person would be you. If so, what makes you you is the continuing mind, not the matter of your body.

Worked example — applying the theory to a case. A nurse cares for someone who has been in the hospital for a month. Ask what the memory theory says about each pair.

The person now, and the person on the day of admission: they remember being admitted, so on the memory theory they are the same person.
The person now, and the person on a night they slept through: they remember nothing of that night, but they remember the days on either side. The theory has to say more about gaps, which is the next section's work.

In words: the memory theory makes personal identity a matter of what a person can remember, and that is both its appeal and the place where it is pressed.

Misconception check — the memory theory is not the body theory. Students often think that being the same person must mean having the same body. It is tempting because we recognize people by their faces. The cure is the variation above. The memory theory says the person goes where the memories go, even into a new body. Locke's view points to the mind, not the matter.

4. Test the memory theory: forgetting and chains

Every position gets its strongest objection. The memory theory faces a sharp one, and you can test it on yourself.

Worked example — the forgetting objection and the chain reply. Test the theory on your own earliest years.

The objection. You remember nothing of being two years old. Yet you seem to be the same person as that two-year-old. If personal identity needs memory, then you are not, which seems wrong.
A second worry. A false memory can feel like a real one. Someone can sincerely "remember" an event they only heard about. So feeling that you remember is not enough; the memory theory needs real memories of your own past.
The reply, from the memory theorist's side. You remember last year. Last year's you remembered the year before. That year's you remembered the year before that, and so on, back toward the child. Overlapping chains of memory link you to the two-year-old. No single memory needs to reach that far.

Here is an honesty note. Philosophers still argue about whether the chain reply answers the false-memory worry. To say a memory is "real", you seem to need to know it is a memory of your own past, which may assume the very identity the theory was meant to explain. The course keys no verdict.

In one plain sentence: the memory theory says you are linked to your past by memory, and its defenders answer the forgetting objection with overlapping chains of memory.

Misconception check — one forgotten year does not refute the theory as its defenders hold it. Students often think the forgetting objection settles the matter, since everyone forgets. It is tempting because the objection is so easy to feel. The cure is to state the view in its strongest form first. The chain version does not need you to remember everything. It needs each stage of you to remember some of the stage before.

5. Meet no-self: the chariot and its parts

The memory theory looks for what links a self across time. Buddhist philosophy offers a very different answer, and it deserves to be met in its own terms.

Think about a river you know. People call it by one name for centuries. Yet the water in it is never the same from one minute to the next, and its banks shift. Nothing in the river stays fixed, and still there is a river to name.

No-self — the Buddhist teaching, called anatta, that there is no permanent self beyond a changing collection of body, feelings, perceptions, mental formations, and consciousness.
Anatta — the Buddhist term for no-self: the teaching that there is no permanent self beyond the changing collection of parts that make up a person.

In Dataset I, the course's set of concepts from four traditions, anatta belongs to the Buddhist tradition and is glossed "no permanent self". The teaching names 5 parts in that changing collection: body, feelings, perceptions, mental formations, and consciousness. Each one changes from moment to moment. On this view, when you look for a self that stays fixed beneath them all, you do not find one, because there is none.

The Questions of King Milinda makes the point with a chariot.

The chariot — the comparison in the Questions of King Milinda of a person to a chariot that is nothing over and above its parts, used to teach that there is no permanent self.

Think of a chariot's wheels, axle, frame, and pole. None of them alone is the chariot. And there is no extra item, the "chariot itself", sitting beside them. "Chariot" is the name for those parts put together. In the same way, on the teaching of no-self, "person" names the changing collection, not a further, permanent thing. The chariot is introduced here and taken up again in Week 14.

Worked example — no-self at its strongest, with its objection. Lay out the view the way its defenders would.

The claim: there is no permanent self beyond the changing collection of 5 parts.
What it explains: why a person can change so deeply over a life, and why looking for a fixed core turns up nothing.
Strongest objection: if there is no permanent self, it is hard to say who remembers, who decides, or who is responsible.
Reply, from the Buddhist side: memory, choice, and their results belong to the changing collection itself, so no further self is needed to carry them. Persons are real; a permanent self is what is denied.

In one plain sentence: the teaching of no-self holds that a person is a changing collection with no permanent self beneath it, much as a chariot is its parts put together.

Misconception check — no-self does not say that nothing exists. Students often think the teaching says that you do not exist, or that nothing is real. It is tempting because "no self" sounds like "no one". The cure is the chariot. The wheels exist, the axle exists, and the parts put together make a working chariot. What the teaching denies is a further, permanent self over and above the parts. It is a precise claim about what a person is, not a denial of persons.

6. Tell determinism from fatalism: the domino line

Now the week's second question. Picture a long line of dominoes. Tip the first, and each one knocks over the next. Given how they were set up and how dominoes fall, the last one had to fall. Some philosophers think the whole world works like that.

Determinism — the view that every event is necessitated by prior events together with the laws of nature.
Fatalism — the view that what will happen will happen whatever anyone does.

These sound alike, but they come apart. On fatalism, it makes no difference what you do: the outcome is fixed no matter what. On determinism, what you do is one of the causes of the outcome. If a domino were taken out of the line, the last one would not fall.

Worked example — the study session. A student says, "If determinism is true, it is already settled whether I pass the exam, so there is no point studying."

What fatalism would say: the result comes whatever the student does, so studying changes nothing.
What determinism says: the result is necessitated by prior events, and the student's studying, or not studying, is among those events.
So on determinism, studying is one of the causes of the result. It is not idle.

In words: determinism does not imply fatalism, because on determinism your choices are among the causes of what happens. Your choices still matter.

Misconception check — determinism is not fatalism. Students often think determinism means "nothing I do makes a difference". It is tempting because both views say the future is fixed. The cure is the domino line. Fatalism says the outcome comes whatever you do. Determinism says the outcome comes because of what happens before, and your choices are part of what happens before.

7. Meet the three positions: hard determinism first

Dataset F, the free will positions, pins 3 standard answers. Each one answers three questions: is determinism true, does free will exist, and are the two compatible?

Free will — the power to make choices that are genuinely up to you, of the kind that moral responsibility seems to need.
Moral responsibility — being the right person to praise or blame for an act, because the act was in the right way your own.

Dataset F: three standard positions on free will, with each one's answer to three questions
Position	Is determinism true?	Does free will exist?	Are they compatible?
Hard determinism	yes	no	no
Libertarianism	no	yes	no
Compatibilism	takes no stand of its own	yes	yes

Read the table as a map, not a scoreboard. Each position has serious defenders, and the course keys no verdict.

Worked example — reading Dataset F row by row. Read each row as a set of answers.

Hard determinism answers yes, no, no: determinism is true; free will does not exist; they are not compatible.
Libertarianism answers no, yes, no.
Compatibilism takes no stand of its own on determinism, and answers yes, yes on free will and compatibility.
The tally on "Does free will exist?": 2 answer yes (libertarianism and compatibilism) and 1 answers no (hard determinism), so 2 + 1 = 3.
The tally on "Are they compatible?": 2 answer no (hard determinism and libertarianism) and 1 answers yes (compatibilism), so 2 + 1 = 3.

In words: only 1 position, hard determinism, says determinism is true. On free will, the yes side outnumbers the no side 2 to 1, versus a 1-to-2 split on compatibility, where 2 positions say free will and determinism cannot both be true.

Incompatibilism — the view, shared by hard determinism and libertarianism, that free will and determinism cannot both be true.
Hard determinism — the view that determinism is true and that free will does not exist, because free will and determinism cannot both be true.

Here is hard determinism in its strongest form. Every choice has causes in a person's brain, body, upbringing, and surroundings. Those causes have causes of their own, reaching back before the person was born. On this view, the more we learn, the more causes we find for what people do. So no choice is free in the sense that praise and blame seem to need.

Now its strongest objection: the view seems to make blame, praise, and deliberation pointless. Why weigh options if every choice is already necessitated? Why thank anyone, or hold anyone to a promise?

The reply, from the hard determinist side: a society can still teach, protect people, and change behavior. Deliberating is still one of the causes of what you do, as Section 6 showed. What goes is only blame that assumes a person could have chosen otherwise.

Misconception check — hard determinism is not the view that people should give up. Students often think a hard determinist must say "nothing matters, so do nothing". It is tempting because the view denies free will. The cure is Section 6. Hard determinism is a view about causes, not fatalism. A hard determinist can still study, plan, and care how things turn out.

8. State libertarianism: open options and the luck objection

Picture yourself at a crossroads in life: two offers, two cities, both good. You weigh them for a week. It feels as if, right up to the moment you decide, both futures are open, and that it is up to you which one becomes real.

Libertarianism — in the free will debate, the view that free will exists and determinism is false; it is a view about choice and causes, not the political view that shares its name.

Here is the view in its strongest form. When you deliberate, more than one option is truly open. Moral responsibility needs that openness: you can be blamed for a choice only if you could have chosen otherwise. Our experience of deciding fits the view, and so does our habit of praising and blaming.

Now its strongest objection.

Luck objection — the objection to libertarianism that a choice prior events do not determine seems to happen by chance, and chance is not control.

Worked example — the luck objection on the crossroads. Suppose your choice of city was not determined by anything before it.

Then, with everything about you and the world exactly as it was, you might have chosen either city.
So what made it this city and not that one? Nothing about you, it seems, since everything about you was the same either way.
That looks like a coin toss inside your head, and a coin toss is not something you control.

The reply, from the libertarian side: the person, not a prior event, makes the choice. A free choice is neither determined by earlier events nor random, because its source is the agent who chooses. The person is the source.

In one plain sentence: libertarianism holds that free will needs open options and that we have them, and its hardest test is explaining how an undetermined choice is controlled rather than random.

Misconception check — this libertarianism is not a political view. Students often read "libertarianism" here as the political view about limiting government. It is tempting because the word is the same. The cure is the definition. In the free will debate, libertarianism is the view that free will exists and determinism is false. It says nothing about taxes, laws, or government.

9. State compatibilism, and test it on hypnosis

Think about two people who hand over their wallets. One is donating to a cause they care about. The other is being robbed at knifepoint. Both acts have causes. Only the first seems free. The difference is not that one act is caused and the other is not. The difference is what kind of cause it is.

Compatibilism — the view that free will is compatible with determinism and that free will exists; it takes no stand of its own on whether determinism is true.

Here is the view in its strongest form. A free act is one that flows from your own reasons and desires, without force or compulsion. An act can be caused and still be free in that sense. That is the freedom people care about when they praise a donor and excuse a robbery victim.

Worked example — the stage show. A volunteer at a stage show is hypnotized. Later, when a bell rings, they stand up and sing.

The compatibilist says the act is not free. It flows from the hypnotist's suggestion, not from the volunteer's own reasons.
Compare a singer who stands up to sing because they love the song. That act also has causes, but it flows from the singer's own desires, so it is free.
A hard determinist answers that every act has causes, and hypnosis only changes which ones. On their view, neither singer is free in the sense responsibility needs.

Now compatibilism's strongest objection: if determinism is true, your reasons and desires were themselves fixed by events before you were born. So in the end, it seems, your act came from those earlier events, not from you.

The reply, from the compatibilist side: freedom asks whether your act came from your own reasons, not whether those reasons had causes. Your reasons are yours even though they have a history, the way your handwriting is yours even though you learned it.

In one plain sentence: compatibilism holds that a caused act can be free if it flows from your own reasons, and its hardest test is the worry that those reasons trace back to causes outside you.

Misconception check — compatibilism does not deny determinism. Students often think compatibilists say that determinism is false. It is tempting because they say free will exists, and the other position that says so, libertarianism, denies determinism. The cure is Dataset F's compatibilism row. On "Is determinism true?" it takes no stand of its own. Its claim is that free will could exist even if determinism is true.

10. Test an argument about free will

Here is an argument from Dataset B, the argument set (illustrative). Its premises were written for teaching, and the course does not endorse them. You met it in Week 2 as an example of a form. Now you can see what is at stake in it.

Worked example — Dataset B, argument 4, in standard form. Lay the argument out line by line, then name its form.

P1: Either free will is an illusion or determinism is false.

P2: Free will is not an illusion.

C: So determinism is false.

Name the form. One option of the "either … or" is denied, so the other follows: that is disjunctive syllogism, from Week 2. Key it: valid. If both premises were true, the conclusion could not be false.

Now the harder question. Is it sound? Soundness is not keyed. Its premises are open questions. Each position from Dataset F answers it differently.

Which premise of Dataset B's argument 4 each free will position accepts or rejects
Position	P1	P2	Its verdict on the argument
Hard determinism	accepts	rejects	Valid, but P2 is false, since free will does not exist.
Libertarianism	accepts	accepts	Valid, and the libertarian accepts both premises.
Compatibilism	rejects	accepts	Valid, but P1 is rejected: free will can be real even if determinism is true, so nothing forces P1's either-or.

In words: the hard determinist rejects P2, the compatibilist rejects P1, and the libertarian accepts both premises. All three agree that the argument is valid. They disagree about its premises.

Misconception check — a valid key is not the course taking a side. Students often read "valid" on argument 4 as the course saying determinism is false. It is tempting because the key sits right next to the conclusion. The cure is Week 2's two questions. Valid only means the conclusion would follow if the premises were true. Two of the three positions reject a premise, so the argument settles nothing until those premises are settled.

11. Run a Frankfurt case: responsibility without alternatives

Libertarians and many others accept a principle that sounds hard to deny.

Principle of alternate possibilities — the principle that a person is morally responsible for what they did only if they could have done otherwise.

Harry Frankfurt's "Alternate Possibilities and Moral Responsibility" (The Journal of Philosophy, 1969) describes cases that challenge it. In his cases, a person could not have done otherwise, yet seems morally responsible.

Frankfurt case — a case of the kind Harry Frankfurt described in 1969, in which a person could not have done otherwise yet seems morally responsible for what they did.

Worked example — a Frankfurt case, in a variation written for this course. The shape is Frankfurt's; the details are the course's.

A person decides, for reasons of their own, to stay late and finish a shared report.
Unknown to them, a device was set to make them decide to stay if they had started to decide to leave.
The device never acts. They decided to stay on their own.
So: they could not have done otherwise, because the device would have made them stay. Yet they seem responsible for staying, since staying came from their own reasons.
If they are responsible, the principle of alternate possibilities is false. That is the challenge.

Now the strongest objection: the device must detect some first sign of a decision to leave, so the person still had one small alternative, to show that sign. Reply, from Frankfurt's side: a flicker that thin is not the kind of choice that responsibility seems to need. No one would praise or blame a person for a passing twitch of a thought.

Why does this matter for Dataset F? If Frankfurt is right, then responsibility may not need the open options that libertarians defend, and a compatibilist can hold people responsible even if determinism is true. A caveat: Frankfurt's cases challenge a principle about responsibility. They do not, by themselves, show that determinism is true or false.

Misconception check — Frankfurt's cases are not about mind control. Students often think the point is that devices or hypnotists can control us. It is tempting because the case has a device in it. The cure is to notice that the device never acts. The case is built so that the person acts on their own reasons, and asks whether the mere absence of an alternative removes responsibility.

12. Ask what a self must be for responsibility

Now bring the two halves of the week together. Picture a jury in a courtroom. They are asked whether the person in front of them is responsible for an act from three years ago. That one question hides two.

Is the person here the same person who acted? That is personal identity.
Was the act free, in the way blame needs? That is free will.

Blaming someone for an act assumes both: that the person blamed is the same person who acted, and that the act was in the right way their own. Each view from this week gives its own account of what a self must be for that to make sense.

What each of this week's views says a self must be for moral responsibility to make sense
View	What links a person to a past act	Is the act free?
Memory theory	Overlapping chains of memory back to the act	Not its question
No-self	The changing collection itself, with no permanent self	Not its question
Hard determinism	Not its question	No, every act is necessitated
Libertarianism	Not its question	Yes, if the person, not a prior event, made the choice
Compatibilism	Not its question	Yes, if the act flowed from the person's own reasons

Worked example — the jury's two questions. Apply the table to the jury's case, one row at a time.

A memory theorist asks whether the person now is linked by chains of memory to the person who acted.
A Buddhist philosopher who holds no-self asks whether the act and its results belong to this same changing collection, with no permanent self needed.
On free will, the hard determinist, the libertarian, and the compatibilist each answer as their row says, and the jury still has to weigh the facts of the case.

In one plain sentence: the ship of Theseus, the memory theory, and the teaching of no-self each give a different account of what stays the same in a changing thing, and hard determinism, libertarianism, and compatibilism each give a different account of whether a caused choice can be free, so both questions stay open and the course keys no verdict on either.

A limitation to keep in view: this week covers only a few views on each question. Your job is to state each one so well that its own defenders would sign it.

Pause and think, choosing one of these two options:

(a) Pick one personal identity view from the table, and write two sentences on how it would explain why you can be held to a promise you made last year.
(b) Pick one free will position from the table, and write two sentences on what it would say to the hypnotized volunteer who asks, "Was that really me?"

Misconception check — these are two questions, not one. Students often treat personal identity and free will as the same debate. It is tempting because both are about the self. The cure is the jury. A person can be the same person who acted and still not have acted freely, as the hypnotized volunteer shows. Keep both questions in view.

Key terms

Numerical identity — Being one and the same thing, so that a thing at one time and a thing at a later time are numerically identical only if they are one thing, not two. (first used: 1. Test the word "same": two senses)
Qualitative identity — Being exactly alike in every quality, as two new phones from one box can be, while still being two separate things. (first used: 1. Test the word "same": two senses)
Identity over time — The question of whether a thing at an earlier time is numerically the same thing as a thing at a later time, after it has changed. (first used: 1. Test the word "same": two senses)
The ship of Theseus — The case, from Plutarch's Life of Theseus, of a ship kept for generations by replacing its old planks with new timber, used to ask whether a thing whose parts are all replaced is still the same thing. (first used: 2. Test a ship: the ship of Theseus)
Personal identity — The question of what makes a person at one time the same person as someone at an earlier time. (first used: 3. Turn to persons: Locke's memory theory)
Memory theory — John Locke's theory of personal identity, which holds that a person at one time is the same person as someone at an earlier time if they can remember that person's experiences. (first used: 3. Turn to persons: Locke's memory theory)
No-self — The Buddhist teaching, called anatta, that there is no permanent self beyond a changing collection of body, feelings, perceptions, mental formations, and consciousness. (first used: 5. Meet no-self: the chariot and its parts)
Anatta — The Buddhist term for no-self: the teaching that there is no permanent self beyond the changing collection of parts that make up a person. (first used: 5. Meet no-self: the chariot and its parts)
The chariot — The comparison in the Questions of King Milinda of a person to a chariot that is nothing over and above its parts, used to teach that there is no permanent self. (first used: 5. Meet no-self: the chariot and its parts)
Determinism — The view that every event is necessitated by prior events together with the laws of nature. (first used: 6. Tell determinism from fatalism: the domino line)
Fatalism — The view that what will happen will happen whatever anyone does; it differs from determinism, on which choices are among the causes of what happens. (first used: 6. Tell determinism from fatalism: the domino line)
Free will — The power to make choices that are genuinely up to you, of the kind that moral responsibility seems to need. (first used: 7. Meet the three positions: hard determinism first)
Moral responsibility — Being the right person to praise or blame for an act, because the act was in the right way your own. (first used: 7. Meet the three positions: hard determinism first)
Incompatibilism — The view, shared by hard determinism and libertarianism, that free will and determinism cannot both be true. (first used: 7. Meet the three positions: hard determinism first)
Hard determinism — The view that determinism is true and that free will does not exist, because free will and determinism cannot both be true. (first used: 7. Meet the three positions: hard determinism first)
Libertarianism — In the free will debate, the view that free will exists and determinism is false; it is a view about choice and causes, not the political view that shares its name. (first used: 8. State libertarianism: open options and the luck objection)
Luck objection — The objection to libertarianism that a choice prior events do not determine seems to happen by chance, and chance is not control. (first used: 8. State libertarianism: open options and the luck objection)
Compatibilism — The view that free will is compatible with determinism and that free will exists; it takes no stand of its own on whether determinism is true. (first used: 9. State compatibilism, and test it on hypnosis)
Principle of alternate possibilities — The principle that a person is morally responsible for what they did only if they could have done otherwise. (first used: 11. Run a Frankfurt case: responsibility without alternatives)
Frankfurt case — A case of the kind Harry Frankfurt described in 1969, in which a person could not have done otherwise yet seems morally responsible for what they did. (first used: 11. Run a Frankfurt case: responsibility without alternatives)

Summary

Numerical identity is being one and the same thing; qualitative identity is being exactly alike.
Identity over time asks about numerical identity across change.
The ship of Theseus asks whether a thing whose parts are all replaced is still the same thing.
Quote Q3 as Dryden's translation of Plutarch, never as Plutarch's own English.
Locke's memory theory ties personal identity to memory; the chain reply answers the forgetting objection.
No-self (anatta) denies a permanent self, not the existence of persons.
Determinism is not fatalism, because your choices are among the causes.
Hard determinism: determinism is true, and free will does not exist.
Libertarianism: free will exists, and determinism is false; its hardest test is the luck objection.
Compatibilism: free will exists and is compatible with determinism; it takes no stand of its own on determinism.
Dataset B's argument 4 is valid by disjunctive syllogism and is never keyed for soundness.
Frankfurt's cases (1969) challenge the principle of alternate possibilities.

Check your understanding

Work these before looking at the answers — they are ungraded, and the answers (with reasoning) are at the bottom of the page.

A town's old stone bridge has had every one of its stones replaced over many years of repairs. A neighbor says, "It's not the same bridge; it's only an exact copy." Which sense of "same" is the neighbor using, and what would a defender of the "same bridge" answer say back?
Sort each claim under the free will position it expresses: (a) "My choice to apologize had causes, but it came from my own regret, so it was free." (b) "Every choice is necessitated by what came before, so no one has free will." (c) "When I choose, nothing before the choice settles it; I do."
A friend reasons, "Either the café is closed or the lights are on. The café is not closed. So the lights are on." Put the argument in standard form, name its form, and say whether it is valid.
A classmate says, "The Buddhist teaching of no-self means nobody exists, so nobody can be blamed for anything." Explain what is wrong with the first part of that sentence, using the chariot.

Answers (worked reasoning — read after attempting)

The neighbor is denying numerical identity: they say the bridge now is a second thing that is qualitatively like the old one. A defender of the "same bridge" answer would reply that the bridge was repaired a stone at a time, kept its shape, its place, and its job, and never stopped being a bridge, so it is one bridge that has changed. Things that are repaired gradually, like a tree that grows, keep their identity while their matter changes.
(a) Compatibilism: this choice was caused but flowed from the person's own reasons, so it counts as free. (b) Hard determinism: determinism is true and free will does not exist. (c) Libertarianism: the person, not a prior event, settles the choice, so determinism is false for that choice.
P1: Either the café is closed or the lights are on. P2: The café is not closed. C: So the lights are on. One option of the "either … or" is denied in P2, so the other follows. That is disjunctive syllogism, which is valid: if both premises are true, the conclusion cannot be false. Whether it is sound depends on whether the premises are true, which you would check by looking at the café.
The teaching does not say nobody exists. Like a chariot, which is its wheels, axle, and frame put together, a person is a real changing collection of body, feelings, perceptions, mental formations, and consciousness. What the teaching denies is a further, permanent self over and above that collection. On the Buddhist view, acts and their results belong to the collection itself, so the second part of the sentence does not follow either.

Next up in this module: the Readings & Resources page, the lecture tutorial, the practice set, the quiz, the discussion, and the assignment. Next week, the midterm review uses one distinction per topic as its method, and Pascal's wager tests whether it is rational to bet on belief.

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