I’ve used the terms qualitative and numerical identity multiple times now, and I notice that you haven’t replied using these terms. What is your understanding of the distinction between these terms and the relevance to the transporter problem?
Because, I don’t think you’re getting this at all, and I’m not sure what’s left to say at this point. We’re not yet having a debate here.
So if I can make a good enough copy of the Mona Lisa, then it literally *is* is Mona Lisa?
No, that’s not how we treat objects.
Many objects might be interchangeable but we don’t say that they are one and the same.
Yeah, I think at this point the specialized terms are obfuscating more than they’re illuminating, so I’ve avoided them. But as I understand it, based on this thread, qualitative identity would be two things that are largely the same, where for practical purposes they are identical. Like two baseballs from the same manufacturer - it doesn’t matter which one you use for the game. Numeric identity is what distinguishes this particular baseball from that other baseball from the same manufacturer.
Is that basically correct?
I confess I Googled that to make sure (I hope) I was getting it right. But one of the examples I found to explain the difference between numerical and qualitative identity is identical twins. Which is a great example: Bob and Dave are identical twins, which means they look alike, and have the same genes, but they’re clearly two different people. They have the same qualitative identity, but different numerical identities.
Except at one point, they were both the same ovum. Two beings who, today, have different numerical identities, once had the same numerical identity - a single fertilized cell.
Am I still using the terms right? The pre-division cell had a single numerical identity, and the post-division cells have two different numerical identities?
So applying this to the transporter problem, I don’t see the logical issue with treating the post-duplicants as two numerically distinct individuals who were both once the same numerically distinct individual. It’s the same principle as identical twins, it’s just changing the point in their existence where the division occurred.
I saw a guy on tv today on one of those reality shows where a couple decorate a house together. In a Make/Female couple the male asked the female for a Phillips screw driver. She said, “what kind of screw driver?”. He said, “Phillips”.
As you can imagine, this went back and forth one or two more times and ended with both a bit more tired and pissed off than before.
First, I thought, “what a dick” it would take two seconds to say, “the cross one”. But then I was ashamed to realize that, I’ve almost certainly had the same conversion with my wife. I was horrified at the way he disrespected and belittled someone for no reason and had to admit that I’ve done the same thing many times.
I like to think of myself as a nice guy and I like to think of myself as a smart guy. I don’t know my IQ but whatever that IQ measures, I feel have in abundance. That has, at times led to pride and arrogance and, unfortunately has sometimes made me disrespectful to people for no good reason. Especially, If I think that, no matter how smart and capable they are, they have a little less of whatever IQ tests measure.
I recognize that this is a failing but I hope no one hates me for it and I hope my victims can try to understand. it’s not really out of malice just carelessness. I can do better.
But Locke’s topic is how you and the twelve year old you and a hypothetical different you are all one and the same individual, a single person, not three. After all, that’s how we use personal identity usually—when you wonder how your life might have turned out if you’d never split up with your high school sweetheart, if you’d taken that job rather than this one, if you’d won a million dollars in the lottery, you’re not thinking about these things happening to different persons, you’re holding to an implicit belief that that person would still be you. Locke is aiming at elucidating the sense in which that’s right, and he points to psychological continuity—sharing memories, experiences, etc.—as the unifying factor.
And this makes sense, at first glance: there can be only one individual that, say, has the memory of your first day in school. Only you experienced that day from your particular perspective, only you had your thoughts, feelings, reactions to it. So we might point to whoever shares in that psychological state as being you, no matter what other experiences and memories might be present. What’s the same across different instances of you makes them you; what differs doesn’t make them not you.
Otherwise, there would be no accounting for the possibility of change: because for something to change isn’t for that something to be replaced by a different thing—that wouldn’t be change—but for something essential about that thing—its identity—to remain fixed, while other aspects change. Your car remains the same thing even if you bump it against a wall, leading to a dent in the bumper. It isn’t suddenly replaced by a different car with a dented bumper.
So, to Locke, your identity, what makes you you, is given by a thread of psychological continuity. Sharing experiences and memories as unique characteristics is what makes something you. That there are also differences just means that you can change, while remaining yourself.
But this runs into the aforementioned issues with duplication, because suddenly, that central supposition ceases to be true.
If somebody were to postulate a theory of personal identity that holds that a single fertilized ovum is a person, and that everything derived from that ovum is the same person, then yes, the same issue would apply. But the upshot is just that that’s a bad theory of personal identity. It is much better simply to say that there initially was one thing—the fertilized ovum—which was replaced by two things in the split. Its identity isn’t preserved, but there’s no reason it should be. If you die, your identity also isn’t preserved; if your car is disassembled into its components, it ceases to exist, with only its parts remaining.
I think I get it. Locke’s saying that the fact that 12 year old me, and current me, share some number of unique memories is how we determine that we’re numerically the same person - sort of like a fingerprint. But if there’s a duplicator, now there’s a copy of me that has the same memories. It’s clearly not numerically the same as me, because there’s two of us in the same room. And that destroys Locke’s definition of self, because those memories are no longer unique, and are no longer proof of numerical identity?
There are two types of duplication which can eliminate the question of ‘numerical identity’ completely. First is the Many-worlds ‘splitting’ concept, where one observer splits into two observers in different timelines. These two observers are identical except for a single event, but they exist in different worldlines, so they could never meet; I suppose that still means they are numerically ‘single’ within these timelines, and so can both be considered ‘the original’ and ‘unique’. I don’t suppose Locke ever even considered that possibility for a nanosecond. In science fiction there are many examples of people meeting their quantum ‘twin’; unlike most forms of duplication, neither instance has the right to consider themselves the original, But I doubt very much that this will ever happen in practice - indeed, the Many-worlds interpretation is very much open to doubt, so ‘quantum twins’ probably can’t happen at all.
The other way that an individual could be duplicated would be by binary fission. A single human could be split by technological magic into two individuals, each with half the body-mass and memories of the other. This would normally be fatal, but perhaps a very clever technosurgeon could achieve this feat. Trouble is, you now have two dwarfs with partial amnesia, neither of which can remember everything about their past life. Not ideal.
Perhaps a sufficiently advanced technosurgeon could replace all the missing body-mass with duplicated cells copied from the other half; you would end up with two chimeras - each consisting of a half-and-half mix of original molecules and duplicated molecules. Hey, it would be difficult, but it is a thought experiment, so anything conceivable is valid, eh? (Incidentally, this particular thought experiment is one that first appeared in this very forum many years ago, but it’s not original to me). A pair of identical individuals created by this sort of binary fission/copying would be truly numerically plural, and also identical in every significant respect.
I should point out that the vast majority of the organisms on this planet reproduce by binary fission, so it is humans who are unusual in that respect. Even humans use binary fission to grow and maintain their body tissues. It may be the case that there are aliens out there who routinely reproduce by binary fission, each daughter retaining all the memories of the parent; they probably wouldn’t look much like us, but that’s not a great problem.
And the great majority of advanced alien civilisations probably include some artificially intelligent entities among their population; entire civilisations might consist purely of AI. Depending on their design, it might be trivial for an AI to copy itself flawlessly.
Robin Hanson has suggested that we might do the same; he describes a kind of human emulation, which he calls an ‘em’, which runs on software and can be duplicated endlessly to perform any difficult task. Maybe the first ‘em’ is nothing more than a pale simulation of its human original, but once you start duplicating the ‘ems’, the questions of numerical and qualitative identity become more-or-less irrelevant.
Close, but I think there are two points worth emphasizing. First of all, psychophysical continuity doesn’t just mean ‘sharing memories’, but more that there’s an unbroken chain of mind-states linking one and the other, so that there is a sense in which your mind-state now is a successor of that of your 12 yo self. A double and you would still share some of the same memories, but your state of mind would not be a successor to theirs, and vice versa.
Also, that continuity isn’t a marker of personal identity, it’s what personal identity consists in. Various things can be used to identify a person, but losing those would not change who they are—just as how losing your fingerprints wouldn’t mean you cease to be yourself. They indicate a person, but aren’t what makes that person that particular person.
In philosophy, one sometimes glosses this in terms of the difference between accidents and essences: your accidental qualities are those that can change with you still remaining yourself, while your essence is that by virtue of which you are yourself, and thus, must remain the same across changes.
So Locke’s psychological continuity is intended to capture what’s essentially you about you, such that everything sharing in that continuity just is you. Duplicates then confound that picture, in that both share in the psychological continuity of pre-duplication you, but neither shares in the other’s, making them both you and distinct from each other.
Ok, but the critical moment is where we have the duplicate and they are still qualitatively identical. Before any divergence. Are they numerically identical?