Dissolving the Thread of Personal Identity

The Trans-Siberian Railway runs for more than 9000 kilometres between Moscow and Vladivostok. Is the Moscow end "the same thing as" the Vladivostok end? Are they "the same thing as" its passage through Novosibirsk?

If one is not puzzled by these conundrums about an object extended in space, I see no reason to be puzzled over the "identity" of an object extended in time, such as a human life.

Pinero pursed his lips and considered. "No doubt you are all familiar with the truism that life is electrical in nature. Well, that truism isn't worth a damn, but it will help to give you an idea of the principle. You have also been told that time is a fourth dimension. Maybe you believe it, perhaps not. It has been said so many times that it has ceased to have any meaning. It is simply a cliché that windbags use to impress fools. But I want you to try to visualize it now, and try to feel it emotionally."

He stepped up to one of the reporters. "Suppose we take you as an example. Your name is Rogers, is it not? Very well, Rogers, you are a space-time event having duration four ways. You are not quite six feet tall, you are about twenty inches wide and perhaps ten inches thick. In time, there stretches behind you more of this space-time event, reaching to, perhaps, 1905, of which we see a cross section here at right angles to the time axis, and as thick as the present. At the far end is a baby, smelling of sour milk and drooling its breakfast on its bib. At the other end lies, perhaps, an old man some place in the 1980s. Imagine this space-time event, which we call Rogers, as a long pink worm, continuous through the years. It stretches past us here in 1939, and the cross section we see appears as a single, discrete body. But that is illusion. There is physical continuity to this pink worm, enduring through the years. As a matter of fact, there is physical continuity in this concept to the entire race, for these pink worms branch off from other pink worms. In this fashion the race is like a vine whose branches intertwine and send out shoots. Only by taking a cross section of the vine would we fall into the error of believing that the shootlets were discrete individuals."

Robert Heinlein, "Life-line"

I was trying to answer the question “Is there any meaningful sense in which I can expect to wake up as myself tomorrow, rather than Brittany Spears?”

What would it be like for you to wake up tomorrow as Britney Spears?

If you mean that someone with your memory and personality wakes up in Britney Spears's body, that is very improbable and we don't need any fancy philosophical gymnastics to see it. If you mean that someone with Britney Spears's memory and personality wakes up in Britney Spears's body (while someone with your memory and personality wakes up in your body) but in some mysterious sense that person indistinguishable from Britney Spears is you, I have to ask whether you really regard that as a coherent proposition.

Personal identity, like most other varieties of identity, is somewhat conventional but not arbitrary. Most of the time, the persons who exist at time t+1 are very similar to the persons who exist at time t -- plus some new ones, minus some deaths, and with a few dramatic changes due to injury and whatnot -- and there's an "obvious" way to assign identities between those times.

The feeling of one's own identity is a bit different (but still somewhat conventional and not arbitrary). You remember doing some things yesterday, while inhabiting a body very much like the one you're in now; those are things you can imagine doing again if you were in the same sort of situation. Accordingly, you regard the person who did those things yesterday as you. Conveniently, this lines up pretty well with the notion of personal identity other onlookers will likely adopt. In weird scenarios where, e.g., you remember two different sets of events from yesterday, or your memories from yesterday are of inhabiting a very different body and doing very uncharacteristic things, you would likely be in some doubt as to whether the memories were "really yours". In some of those weird scenarios (e.g., as you're pondering the question, a chap in a white coat says "aha, it seems my experimental memory-implantation procedure has worked!") you would probably decide that they weren't. In others (e.g., what you remember yesterday is being in a wolf's body and chasing people, and a different chap in a white coat is now explaining that lycanthropy turns out to be real after all) you would probably decide that they were "really yours" but be tempted to say that "I wasn't really myself then". But these things are all somewhat conventional and they all admit of degrees.

Perhaps I've just been thinking about this stuff for too many years, but for me it's all in the category of "slightly disturbing but pretty much obvious". Perhaps that's where it will end up for you too :-).

Here's a thought experiment:

Let's say evil sadistic scientists kidnap you, bring you into their laboratory, and give you two options:

A: they incinerate your brain.

OR

B: they selectively destroy almost all of the neurons in your brain associated with memories and somehow create new connections to create different memories.

Which option would you choose?

If you see any reason to choose option B over option A, then it would seem to me that you don't really buy into "pattern identity theory" because pattern identity theory would suggest that you have effectively died in scenario B just as much as scenario A. The pattern of you from just before the operation has just had a discontinuously abrupt end.

Yet, I would still choose option B because I would still anticipate waking up as something or somebody that next morning, even if it were someone with a completely different set of memories, preferences, and sense of self, and surely that would be better than death. (Perhaps the evil scientists could even be so kind as to implant happier memories and healthier preferences in my new self).

Is this anticipation correct? I don't see how it could be wrong. Our memories change a little bit each night during sleep, and still we don't NOT wake up as at least someone (a slightly different person than the night before). I fail to see how the magnitude and/or rapidity of the change in memory could produce a qualitative difference in this regard. If it could, then where would the cut-off line be? How much would someone have to change my memories so that I effectively did not wake up the next morning as someone?

Note that this discussion is not just academic. It would determine one's decision to use a teleporter (especially if it was, let's say, a "1st generation" teleporter that still had some kinks in it and didn't quite produce a 100% high-fidelity copy at the other end). Would such a 99% accurate teleporter be a suicide machine, or would your subjective experience continue at the other end?

In any case, pattern identity theory (which says the continuation of my subjective experience is attached to a continuation of a particular pattern of information) seems out the window for me.

Nor does some sort of "physical identity theory" (that posits that the continuation of my subjective experience is attached to the continuation of a particular set of atoms) make any sense because of how patently false that is. (Atoms are constantly getting shuffled out of our brains all the time).

Nor does some sort of "dualism" (that posits that the continuation of my subjective experience is attached to some sort of metaphysical "soul") make any sense to me.

So at this point, I have no idea about under what conditions I will continue to have subjective experiences of some sort. Back to the drawing board....

Personal identity = changing slowly, so it doesn't feel like disapearing.

The root of the problem is, that concepts like "the same thing" are ill defined in every day vocabulary. So, pretty much everyone is confused when asked the above questions.

Will I be the same, even after I forget everything? In fact, I have already forgotten much of the data. And I certainly don't invoke all my existing memories to identify myself as myself.

The basic definitions people have, are flawed.

It is nice to see people thinking about this stuff. Keep it up, and keep us posted!

Have you read the philosopher Derek Parfit? He is famous for arguing for pretty much exactly what you propose here, I think.

Doubt: Doesn’t this imply that anthropic probabilities depend on how big a boundary the mind draws around stuff it considers “I”? Self: Yes. Doubt: This seems to render probability useless.

I agree with Doubt. If can make it 100% probable that I'll get superpowers tomorrow merely by convincing myself that only superpowered future-versions of me count as me, then sign me up for surgical brainwashing today!

If you take altruism into account, then it all adds up to normality. Or rather, it can all be made to add up to normality, if we suitably modify our utility function. But that's true of ANY theory.

My question is, would you apply the same principle to personal-identity-right-now? Forget the future and the past, and just worry about the question "what am I right now?" Would you say that the answer to this question is also mind-dependent, such that if I decide to draw the reference class for the word "I" in such a way as to exclude brains in vats, then I have 0% probability of being a brain in a vat?

At any given time my ability to focus on and think about my individual memories is limited to a small portion of the total. As long as the thread of connections was kept consistent, all sorts of things about myself could chance without me having any awareness of them. If I was aware that they had changed, I would still have to put up with who I had now become, I think... unless I had some other reason for having allegiance to who I had been... say disliking whoever or whatever had made me who I was, or finding that I was much less capable than I had been, or something. If I was aware that they would change, drastically, but that afterwards it would all seem coherent, and I wouldn't remember worrying about them changing - or that while I was not focusing on them, they were changing very radically, and faster than normal, that would seem very deathlike or panic-inducing I guess.

Excellent :). This significantly mirrors my recent thoughts (though I used slightly different terminology), I outlined my plans for a mini sequence in the open thread a few days ago, asking for people to help look over things.

The core similarity is what I call the pattern theory of identity, which, justified by pretty much exactly your reasoning, concludes as you do that "I" is a moving fuzzy category, and additionally that category is usefully defined by "aspects of current-me which current-me values".

I've developed it a bit further and have a load of fun links to explore, to morality, evolution, and a bit more on decision theory.

Would you be interested in working together on writing up and developing a little series of posts based on this? It seems to me to effectively dissolve several things which are otherwise confusing, even beyond the parts you've already covered, which are already important.