John Locke, personal identity and the problem of duplication

Great Debates
61

Because shared understanding of what makes for a numerically identical consciousness is the bedrock of much of human society.

Am I the same person I was twenty years ago? In many ways no. Superficially I’m balder and creakier. Less superficially I have very different ideas about everything from relationships to politics. Put me in a situation I was in 10 years ago and I would likely choose very differently.

Yadda yadda yadda. Am I the same person who signed for a mortgage twenty years ago? Oh hell yes. All the qualitative changes in the world won’t let me wriggle out of that one. The guy who signed and the guy who’s paying now are one and the same. Same with non-legal agreements. Same with relationships. I am the me of twenty or ten or five or one year ago and if we were all to start acting like that wasn’t true it would be anarchy.

So, let’s put some money on the table: You, @Sam_Stone, find a magic ring that purports to duplicate the wearer. Being cautious, you want to test it in a human guinea pig. Being reckless, I agree to be your testee for $1000. We sign a contract to that effect. I put on the ring. There is a blinding flash and when you can see clearly again lo! there are two @Stanislauses before you.

“Well”, says the one on the left, “That seemed to work fine. I’ll take the money in cash if that’s ok with you.”

“Woah there handsome,” says the one on the right. “I’m the one who signed the contract. I’ll take the cash.”

“Don’t talk nonsense you good-looking fool,” says Lefty. “I have a very clear memory of signing the contract, I did it then I put on the ring. I’m the one who gets paid.”

So, who do you pay? Both of them will swear on oath that they have a continuous consciousness from signature to duplication. You don’t know exactly how the ring works so you don’t know which if either is physically continuous with the contract signer. Do you
a) pay neither of them. The contract signing @Stanislaus ceased to exist when he put on the ring and neither of these guys in front of you now made any deal with you.
b) pay one of them $1000 dollars. One of them is the contract signer in exactly the same way that you are the guy who signed your last contract. You did it then, you kept existing, you are that same guy now. Same here.
c) Pay both of them $500. They are both jointly the person who signed the contract and that person, though now bifurcated, has a legitimate claim to $1000.
d) Pay both of them $1000. They are both separately the person who signed the contract and thus they both have a legitimate claim to $1000.

Of course, option b) comes with the extra wrinkle that you have to decide which one is numerically identical with the contract signer. How would you do that?

62

(Call it self interest, but I really don’t see how to avoid option d)

63

Someone has a debt. They get married. Now their debt is shared by their spouse and can be collected from either, but not from both.

Did Locke actually address this issue? Seems unlikely to me given the state of human duplication technology at the time. I think the idea of a reverse transitory effect that requires all things to have unique pasts doesn’t exist, and isn’t needed simply for the concept of duplication.

However, if your duplicator doesn’t produce two identical indistinguishable copies but instead works by producing an original and a copy there are questions of identity for the copy. In that case we would be looking at not simply continuity of consciousness but continuity of material existence as well. And that case presents a more difficult case of identity to resolve.

64

I’ll try again to explain the issue, because I think we’re back on semantics, if we’re talking about practical issues like how debt or wealth gets divided.

Right now, I am alive. I am getting to see, hear and experience the universe. My continued existence is the most important thing to me.
I couldn’t care less how many Mijins there are in the universe. Right now, in our universe, it happens to be the case that talking about Mijin’s existence, and my consciousness, are one and the same thing.

But in the various hypotheticals, that doesn’t necessarily follow.

If there’s an identical Mijin to me, somewhere in a galaxy far, far away…so what? I don’t think I will wake up as him any more than I would wake up as any other person.

The reason I don’t wake up as George Bush tomorrow is not because he’s not similar enough to me, it’s because he’s a separate entity to me and there’s no mechanism by which consciousness “jumps”.

65

Since there is nothing special about, or no difference between similar elemental particles, it is theoretically possible to exactly replicate a brain and create more than one mind/brain with no measurable differences between them. They should be exactly the same to all observers, in all respects. But, they’re not.

There is one difference that no one can measure…except the original and replicated minds themselves. They know they are not the same in one important respect—they each have independent personal identities (PIs). They are self-aware in only one brain. They experience qualia in only one brain. They are separate, independent people, each with his own PI. If they were the same, they would perceive sensory input and be self-aware in all replicated brains combined, like a wired network. But, they can’t.

How can 2 or more minds be exactly the same, yet different in one respect?

Thought Experiment: Put person A in an enclosed room and replicate both he and the room exactly, all the way down to the quantum level. Let’s call the replicated person in the replicated room “B”. Both A and B are exactly the same to all outside observers at the moment of replication, and they should remain exactly the same going forward in time since they are both in exactly the same environment. They each receive exactly the same sensory input, in exactly identical brains, so there should be no bifurcation or splitting into separate individuals, right? Yet, they do (I’m pretty sure they do. How could they not, without being connected?).

Now knock on the door of room B only. For the first time, A and B receive different sensory inputs. Is this the point that they bifurcate into unique individuals and become independently self-aware? No, that makes no sense. That would mean B changed his PI at the moment you knocked on the door. That’s absurd. It only makes sense that they were unique individuals from the moment of replication, not afterward. 2 exactly the same minds with exactly the same sensory input, with no measurable difference between the 2 to all outside observers, yet they are different.

I believe the answer to this apparent paradox is, although the two brains are exactly the same, in identical environments, receiving identical input, they do not occupy the same spatial coordinates—they never did. They are separated in space, and that is the difference that allows separate PIs to emerge from each identical brain.

Both minds are self-aware (SA), but their SA supervenes on one brain only. Once self-awareness emerges in a brain, it is bound to the brain it emerged from, and it continues unabated. Maybe it’s possible to transfer your self-awareness (e.g into an AI), but it can’t be split in two, and it can’t be in two places at once. There is continuity once SA is achieved shortly after birth, until brain death. You can be unconscious (e.g. sleeping, general anesthesia, “dying” and being revived…) and retain your original PI, but at no point in your life are you non-conscious. Break that continuity of consciousness and I believe you will break your PI forever.

Anyway, that’s how I solve the paradox of two exact brains not being exactly the same. And, that’s why I won’t get into a Star Trek transporter. I may become an AI droid though. That would be mind-blowing fun.

66

Was I gone? (But thanks anyway.)

However, I apologize for dumping my sour grapes like that. It’s itself a cheap ploy to dominate a discussion, even if it’s sometimes justified.

Exactly: on Locke’s theory, the clone and the original would not share a psychological continuity, and hence, they’re different persons.

The trouble is just that, on Locke’s theory both the original and the copy would likewise be the same person. Because, due to psychological continuity, the person with experiences A+B+C…X+Y is the same as the person with experiences A+B+C…X+Y+Z, in the same way you’re the same person now you were at age 12. That’s what Locke’s theory is about, after all: to elucidate what makes it so that we remain the same persons across the changes brought on by time.

But then, likewise, the person with experiences A+B+C…X+Y+ Ꙃ is the same as the person with experiences A+B+C…X+Y. After all, there is just as much continuity there: that person has just as much cause to say ‘that’s me three days ago’, or whatever. But identity is transitive: if A = B and B = C, then A = C. But then, since both post-clone persons are identical to the pre-clone person, they’re identical to one another.

Hence, on Locke’s theory, duplicates both are and aren’t the same person: a contradiction.

67

Because they now have (slightly) different memories, they are (slightly) different people, and therefore there is no contradiction.

. I retract my previous statement; Locke’s theory applies, even to a magically exact copy, or a copy produced due to Many-Worlds splitting. I’m not sure it is the whole truth, but it does seem hold part of the truth.

68

I’m fairly sure that the root problem here is reification. Many people who contemplate personal identity and consciousness think that they are physical and durable things, items that exist in some concrete form somewhere. They aren’t really things - they are on-going processes, which change all the time in response to the environment.

You can’t simply expect an individual at time T1 to be the same as that individual at time T2; they will have changed in that time, inevitably.

69

They’re not, at least not according to Locke’s theory. Again, the purpose is to elucidate how you, now, are the same person as you at age 12. Not somewhat similar, not kind of like, but the same: identical as a person. And that, Locke claims, is because of psychological continuity. The older you clearly has many experiences the younger you lacks, but it’s sufficient for both of them to be the same that there is a thread of psychological continuity between the two.

70

Well, in that case I go back to saying he was both right and wrong.

If I were to be split into two individuals (two dividuals?) by a magic technowizard, or by the Many-Worlds interpretation, then I (we) would both have psychological continuity with our past self.

We two copies are not completely identical, because one dividual has a memory of Z, and one has a memory of Ꙃ. But we both have psychological continuity up to that point.

71

No, I think everyone get that. The issue is that you’re thinking about it as an event that happened in the past. If five years ago, someone created a perfect copy of you on Mars, learning that today doesn’t have an implications on the identity of the Mijin that stayed on Earth. I think everyone in the thread is broadly agreed with that.

But what about if the duplication is something that’s going to happen in the future? Someone says, “If you step into this device, it will create a perfect copy of you, including all your memories, on Mars.”

Is the Mijin who stays on Earth the same person who stepped into the duplicator? Yes.

Is the Mijin who steps out of the duplicator on Mars the same person who stepped into the duplicator on Earth? Also yes.

Is Earth!Mijin, post-duplication, the same person as Mars!Mijin? No.

72

So you’re saying that A=B, C=B, but A\ne C. I.e., two things can be identical to one thing, without those things being identical to one another.

Why should anyone believe this is a notion of ‘identity’ at all? Clearly, it’s not how the notion is used in everyday discourse. Identity, after all, should imply that whenever you use one (at least in statements relevant to identity), you could equally well substitute the other; but that fails on this notion.

73

No, because neither of the post-duplicates is identical to the pre-duplicate. One duplicate is the original, plus the experience of stepping out of the duplicator and still being on Earth, and the other is the original, plus the experience of stepping out of the duplicator and being on Mars.

74

The way I look at it is, I believe I have a future in the person who wakes up in my bed tomorrow (…me, not a hookup), but I don’t have a future in any copy of me, whether it is someone with my re-created brain on Mars, or post-transporter, or anywhere else. Because, if my brain can be re-created once, it can be re-created multiple times—it’s simply a configuration of particles arranged similarly to my brain. All copies are.

Can you be self aware in multiple bodies all at once? No, therefore if you don’t have a future in one copy, you can’t have a future in any copy, because for all intents and purposes, they are all the same, and they are all different from you.

Whats different about my mind in my original brain in bed tomorrow, as opposed to all the copies? Continuity of the process of self-awareness in my local brain. All copies likewise have their own PI, which started the moment they were created, and continue on their own course.

75

You seem to be trying to have your cake and eat it, too:

Either, in both cases, they are the same person (numerically identical, i.e. not two persons): then you’ll also have to admit, by any reasonable notion of identity, both to be the same, period. Or, they’re not the same: then you’re just disagreeing with the notion that psychophysical continuity suffices for identity, i.e. Locke’s theory.

76

Which you can totally do if you have access to a duplicator.

No, I don’t think I do. They’re both the same person as the person who entered the duplicator, because of psychological continuity. They’re different from each other, for exactly the same reason.

77

Depends on which one is your cake.

But then, again, you’re giving up transitivity: if they’re the same as the person stepping in, they’re the same as each other, just in the same way you at 20 and you now are the same person by virtue of both of them being the same as you at age 12: there is numerically only the one you. It can’t both be true that there is only one, and that they are different.

78

I’m the same person I was when I was 12, plus X, where “X” is several decades of accumulated experience. If you could take me when I was 12, and instead add Y, where Y is several decades of different experiences, I’d be a different person right now. But in both cases, I was the same 12 year old before you started adding different sets of experiences.

How does transitivity work with identical twins? There was a single fertilized ovum, it split, and then there were two fertilized ova. Under the way you’re invoking transitivity, it seems only one of them was the original cell, and the other is something entirely unrelated.

79

Respectfully, I don’t think so.

…and that’s one position a person can take on the transporter problem. There are at least three philosophical positions on this problem. The fact that you’re asserting this as a premise that I would trivially agree with, suggests to me that you are still not seeing the distinction between qualitative and numerical identity.

Because your assertion is essentially that qualitative == numerical identity, which is a pretty bold claim (and also contrary to how we treat all other objects; anything that’s not a conscious human).

80

It certainly looks like it from here. I mean, you also mentioned this:

The fact that you’re talking about consciousness “jumping” suggests you’re missing a key part of the position against which you’re arguing.

I wasn’t suggesting it as something you would agree with. I was stating it as an explanation of my position.

I’m treating them just like I’d treat any other object that’s been run through a duplicator. Throw a hat into it, and ask me which one is the original, and I’ll have the same answer.