Metaphysics II: Personal Identity

This is Unit Five of Philosophy: the second metaphysics unit, on personal identity. Look at a photograph of yourself at five years old. Not one cell in that body is still in yours. The beliefs are gone, most of the memories are gone, the size is unrecognisable. Something nonetheless makes that child you, and the unit asks what that something could be. This is not the question people mean by finding themselves. It is not about character or authenticity. It is about what has to hold for a person now and a person later to be one person rather than two. A great deal rests on the answer. We imprison people for crimes committed decades ago. We save money for someone we have never met, who will be old. Both practices assume a person persists — and if the answer turns out to be thin, those practices need new foundations. Four answers get built, each broken by the next. Then one problem that breaks all of them at once, and a philosopher who responds by suggesting the question was not worth what we thought. By the end you will be able to do five things. One: tell being one and the same thing from being exactly alike, and say why the puzzles need the distinction. Two: state the objection that asks how soul persistence could ever be checked. Three: state the objection that catches memory in a contradiction, and the repair. Four: state the duplication problem, and the response that dissolves it. Five: test a theory by criterion, clean case, then duplication.

Two entries to fix what is being asked and why it is not idle. The second is the one that gives the unit its weight — several ordinary practices turn out to presuppose an answer that nobody in the unit manages to supply cleanly.

The question.

Philosophy 0185 The Question of Personal Identity

What makes a person now and a person then the same person. And note the register: this is not the search for who you really are — that is a different project entirely.

What rests on it.

Philosophy 0186 What Hangs on the Answer

We jail a man for something done long ago, and you set money aside for a pensioner you have never met. Both assume somebody persists — and if that assumption turns out shallow, both need rebuilding.

One piece of vocabulary and one ancient problem. The vocabulary looks pedantic until the thought experiments arrive, at which point running the two senses together destroys every one of them.

Two senses of the word.

Philosophy 0187 Numerical and Qualitative Identity

Twins can be indistinguishable and are still two people; you yesterday and you today are one. This unit asks about the second relation only — and an exact copy is never automatically you.

The ancient problem.

Philosophy 0188 The Ship of Theseus

Replace a ship's timbers one at a time until nothing original remains. Then assemble the removed ones into a second ship. Two candidates, one history, and somebody owes a verdict.

The oldest answer, and an objection that does not argue souls do not exist. It argues something more awkward: that whatever we actually use to identify people, it cannot be that.

The answer.

Philosophy 0190 The Soul Theory

An immaterial thing that persists while the body ages and the memories fade — the same passenger throughout, whatever happens to the vehicle.

The objection.

Philosophy 0191 The Verification Objection

You identify a friend by face, voice, recollections and manner. Exchange the immaterial part without telling anyone and every piece of that evidence reads the same. So whatever we track daily and confidently, it is not that.

The answer everyday life runs on — and the thought experiment that has powered every body-swap story since it was written. The refinement offered in response is worth watching, because it gives away the argument while appearing to save it.

The everyday answer.

Philosophy 0192 The Body Theory

One living body persisting is one person persisting, which is how identification actually works in practice. Though the ship problem is already waiting — matter is replaced continually and the body carries on regardless.

The case against.

Philosophy 0193 The Prince and the Cobbler

Put one man's recollections and character into another man's body, and nearly everyone says the first man is now living there. Every story of this kind since has run on that same reaction: we follow the mind.

And the refinement.

Philosophy 0194 The Brain Criterion

Identity follows the organ carrying memory and character. But notice what has been conceded — the organ matters because of what it carries, which invites dropping the organ and keeping the contents.

Dropping the substance entirely: identity carried by recollection. Then an objection that does not appeal to intuition at all — it catches the theory violating a rule of logic — and the repair that answers it.

The theory.

Philosophy 0196 Locke's Memory Theory

You are the earlier person whose experiences you can recall, and substance drops out entirely. Remembering your first day at school is what makes that child you.

The objection.

Philosophy 0197 The Brave Officer Objection

A general recalls being a young officer; that officer recalled being a boy; the general recalls nothing of the boy. If the first is the second and the second the third, the first must be the third. Memory delivers a contradiction.

The repair.

Philosophy 0198 Psychological Continuity

Chains of overlapping memory, character and intention, with no requirement of recalling every stage directly. A rope reaches its far end without any single fibre running the whole length.

Now the difficulty that does not target any one theory. Any criterion built out of psychological facts can, in principle, be met by two people at once — and one person cannot be two. Then a response that accepts the whole problem and denies it costs anything.

The problem.

Philosophy 0199 The Duplication Problem

A transporter fails to disassemble the original while building the copy. Both are continuous with the person who stepped in, both make the claim — and one thing cannot be two things.

And the response.

Philosophy 0200 Identity Is Not What Matters

What is worth wanting was the continuity itself, not winning the one-place contest. If a copy wakes with your memories, projects and loves, ask precisely what the original lost that mattered. This dissolves the question rather than answering it, and many find that harder to accept than the problem.

Three entries that step outside the contest. One says the self is composed rather than discovered. One reports that looking inward finds no self at all. And the third notes that a tradition on the other side of the world reached that second conclusion first, by the same route.

A self that is composed.

Philosophy 0201 The Narrative Self

Origins, turning points, and aims, assembled into an account that holds a life together. The theory takes the story to be the binding. Note that this answers what unifies a life rather than the question the unit has been asking.

A self that is not found.

Philosophy 0203 Hume's Bundle Theory

Look inward for the self and you catch a sensation, a sound, a thought — never the thing doing the catching. On this report a person is the experiences rather than their owner.

And the tradition that got there first.

Philosophy 0204 The Bundle and Anatta

Two traditions with no contact reach the same denial by the same introspective route. But agreement is not sameness: one anchors an ethics and a practice, and the other found the result unsettling and moved on.

One procedure, and its steps come in an order people reverse. The temptation is to go straight for the exotic case, because that is where theories break — but a theory that was never run on an ordinary case has not been examined.

Watch a theory get tested.

Philosophy 0208 Testing a Theory of Identity

Pull out what the theory says identity consists in, run it on a straightforward scenario, then put two claimants in front of it. The clean case comes first — a theory not tested on the situation it was built for has not been tested.

Five things you can now do. You can tell being one and the same thing from being exactly alike, and you know the puzzles need it — an identical copy is never automatically you. You can state the objection to the soul theory: swap the soul secretly and every piece of evidence anyone uses reads the same, so that is not what we track. You can state the brave officer objection — memory's verdicts contradict each other across three stages of one life — and the repair that runs overlapping chains instead of direct recall. You can state the duplication problem, which defeats any psychological criterion, and the response that says the one-winner contest was never the thing worth wanting. And you can test a theory in order: extract the criterion, run the ordinary case, then introduce a second claimant.