Wolfgang Schwarz :: Pre-fission possibilities

Pre-fission possibilities

Posted on Friday, 26 Mar 2010.

Suppose tonight you will fission into two persons. One of your successors will wake up Mars and one on Venus. There are then two possibilities for how things might be for you tomorrow: you might wake up on Mars, and you might wake up on Venus. These are distinct centered possibilities that do not correspond to distinct uncentered possibilties. There is just one possibility for the world, but two possibilities for you. Indeed, the two possibilities are two actualities: you will wake up on Mars, and you will wake up on Venus. It is tempting to go further and say that there are also two possibilities for you now. I want to discuss three quite different reasons for making this move.

The first comes from intuitions about attitudes: when you think about your situation, couldn't you wonder where you will wake up? Couldn't you hope that it will be on Mars? Couldn't you imagine having the future on Venus? If the content of your wondering, hoping and imagining are centered possibilities, then these possibilities must have a unique, determinate future: since your hope to wake up on Mars differs in content from your fear to wake up on Venus, there must be one centered possibility verifying "I will wake up on Mars" and another verifying "I will wake up on Venus".

Dilip Ninan offers this motivation in his recent paper "Persistence and the First-Person Perspective", and he cites several authors who apparently put forward similar intuitions. I have to admit that I don't share these intuitions. In fact, they seem clearly false to me. If you wonder where you will wake up, you have misunderstood your situation. Perhaps you think you are a non-physical soul that won't fission at all. But that's not your actual situation.

If there were two pre-fission possibilities, it should make sense to ask which of them obtains. But the only sensible anwer is 'both'. And then you can't reasonably wonder which of them obtains. Moreover, if the two possibilities are genuine alternatives, it should be possible (in principle) to learn which of them obtains. But if you understand your situation, you know that anyone who comes along and tells you that you'll wake up on Mars and not on Venus is a liar. Even if it is God.

So the first reason doesn't work.

The second reason for postulating distinct possibilities comes from certain views about the metaphysics of people and the nature of centered worlds. On the popular "worm" view, there are two people in the fission scenario, one who wakes up on Mars (call her M) and one who wakes up on Venus (V). Both M and V exist today, although they somehow coincide. If centered worlds are something like world-time-individual triples, then we naturally have two possibilities at times t before the fission: <w,t,M> and <w,t,V>.

Something like this reasoning can be found in recent papers by David Wallace and Simon Saunders. I find both steps unconvincing. I don't believe in the worm view of persons, and I don't think centered worlds can be modeled as triples of a world, a time and an individual.

But the issue is subtle. Let's say that a centered world is a maximally specific way things might be, or a maximally specific property. Such a property must include historical information: "x is presently F and G and H" is less specific than "x is presently F and G and H and will be J and used to be K". So a maximally specific property can't be silent on whether and where x will wake up tomorrow. However, among the maximally specific futures a thing can have is to wake up both on Mars and on Venus. For instance, consider your present time-slice S. A maximal specification of S's properties would include having successors on both Mars and Venus. Or consider the fusion F of V and M. A maximal specification of F's properties would include having future parts on both Mars and Venus.

Lewis once suggested that although fissioning involves two persons M and V, any pre-fission thinking and wondering is done by a stage S that is common to M and V. This seems to imply that if you believe that you are temporally extended, then what you believe is false: the belief content is a class of extended objects, but the believer is unextended; so the content is false. Better say that what does the thinking and wondering is the fusion F; then your belief that you exist tomorrow on Mars is true, and so is your belief that you exist tomorrow on Venus.

Apart from S and F, of course the two worms M and V also exist, as do their maximally specific properties. But I don't think you can reasonably believe or hope to have one of these properties rather than the other. Compare the gerrymandered fusion of your present stage S together with some past stages of the Eiffel tower and some future stages of Barack Obama. You can't reasonably wonder whether you are this object rather than some other, equally gerrymandered fusion (unless, of course, you misunderstand your situation e.g. by thinking that only one of those fusions exists).

So the second reason also doesn't work.

Not only that, in both cases the relevant considerations seem to support exactly the opposite conclusion: that your distinct future possibilities do not correspond to distinct present possibilities.

This is unfortunate, because distinct pre-fission possibilities would be very convenient for the epistemology of branching subjects. They would help a lot to simplify my centered form of conditionalisation, and they might be useful in the confirmation theory of quantum mechanics (this is what Wallace and Saunders use them for). That's the third reason.

Comments

# Shen-yi Liao on 27 March 2010, 05:46

Hi Wo,

I am very sympathetic to the claim that centered worlds cannot be modeled as (w, i, t). But I am a little puzzled by the objection you have against the first reason you mention. I think your intuition about which one you are is right. However, why isn't `both' a legitimate answer to `which one obtains?'?

Compare: suppose there is an older man and an older woman in a room with me and my friend. My friend asks me `which one is your parent?' and I answer `both'. That sounds okay to me. So the reason that `both' is not a legimitate answer cannot simply be that `which' forces the choice or either one or the other. Can you say more why you don't think `both' is a legitimate answer in the fission case?

Furthermore, if `both' is a legitimate answer, then that's good reason for us to think that there are indeed two distinct possibilities.

# wo on 27 March 2010, 15:04

Hey Sam,

one worry is that if two possibilities are both realised, then at least one of them isn't maximally specific. But the two pre-fission possibilities were supposed to correspond to different centered worlds.

The other worry is that if you know that two possibilities A and B are both realised, you can't sensibly hope or believe or imagine that (under these circumstances) A rather than B is true. And that was supposed to be the intuition.

# Mark Moyer on 25 May 2010, 22:10

Hi Wo,

I'm not sure I understand your post. I share your intuitions (see my "A Survival Guide to Fission" in Phil Studies, 2008). According to my intuitions, a) the person will be on Mars and yet b) the person will be on Venus. Are you saying that given these sorts of intuitions, the case the opponent's raise doesn't make sense? If so, I entirely agree.

Or are you saying that even if you have the opposite intuition (that it is not the case that the person will be on Mars and that the person will be on Venus) that their case doesn't make sense? If so, I don't see this. The Lewisian picture seems consistent to me. Any wondering that M does prior to fission is, of necessity, wondering that V does (except that first person indexicals pick out different referents) since the wondering is done in virtue of the states of the slice S that they share. Thus, prior to fission both M and V can hope that they (respectively) are the one on Mars. Both can hope to be on Mars, and both will find out if their hopes were satisfied (M's will be, V's won't). Both futures are realized, but you can hope that you will go to Mars because this is just to hope that you are M. One of you is, one isn't. I don't see the problem with this (other than conflicting with intuitions about personal identity).

Mark

# wo on 26 May 2010, 19:52

Thanks Mark,

yes, I want to say that M and V cannot coherently hope that they are M, or wonder whether they are M, unless they are seriously mistaken about their situation. I guess this is partly motivated by the intuition you mention. But also by the idea that "disambiguated worms" like M and V are not proper subjects of attitudes: what does the wondering and hoping isn't M or V (or both), but either their fusion or their common stage. We can sensibly speak of M and V wondering and hoping because they are associated with this stage or fusion. But in this respect, they are on a par with (for example) the upper half of my body, or with the upper half of my body together with this sofa here. A hope to be M is like my hope that I am the upper half of my body, or that I'm the upper half of the body together with the sofa. Such a hope strikes me as incoherent, unless I'm seriously mistaken about my situation.

I'll have a look at your paper.

# Mark Moyer on 26 May 2010, 20:18

Hi Wo,

That helps me get straight on your view, but I'm unsure *why* you think M and V can't be subjects of attitudes. It strikes me as an interesting thought, but I can't come up with any reasons myself. To me it's more the idea that M and V can't be the *object* of attitudes (i.e., attitudes about persons). That is, as I see it, when I think of that pre-fission person sitting there, by the fact that there's one stream of consciousness it must be one person, and if there are two streams of consciousness that are continuous with it, ipso facto that person has two futures. So I'm very much in agreement with you, but I think my thinking all rests on the intuition about what it is to be a person and on the idea that with fissioning streams of consciousness the person before you will be on Mars and yet will be on Venus.

But this is just to emphasize that if there's some line of thinking riding on what is the *subject* of experience, I'd be very interested. (As I see it, the subject thinks of herself by thinking of a person, so whatever the subject is, the referent of her use of 'I' would still have to fit the concept of a person and, by my thinking, have to be the fusion of M and V.)

Of course, we aren't alone in thinking that the person sitting there before fission is correct in saying "I will by on Mars" and also "I will be on Venus". The stage theory (Sider and then Hawley) also employ this intuition. And Perry motivates his theory in part by this, if I remember correctly.

# Alastair Wilson on 10 November 2010, 22:19

Hi Wo,

Just found this. I like the way you set things up.

On the first reason. Intuitions divide sharply on this. Whether or not Ninan and co's intuitions, or your intuitions (which are shared by many people), are 'correct' is clearly disputable. But either way it seems that intuitions of this sort are just too shaky to motivate the two-distinct-possibility view.

On the second reason. I'm not sure I get this argument:

"Compare the gerrymandered fusion of your present stage S together with some past stages of the Eiffel tower and some future stages of Barack Obama. You can't reasonably wonder whether you are this object rather than some other, equally gerrymandered fusion."

Imagine that the gerrymandered fusion (call it A) you mention is conscious. Then A could wonder about which gerrymandered fusion it is (and the right answer would be A.) Ruling this out seems to require ruling out that A could be conscious.

Isn't that what's really doing the work in your argument - that worms are just the wrong sort of things to be ascribed mental states? If so, plenty of people would agree with you (including I think the mature Lewis, and also Paul Tappenden who has written several critiques of Saunders and Wallace) - but Saunders and Wallace would dispute the point. They (in their 2008 paper) are explicit that they're ascribing mental states to whole continuants and argue that this is a benign kind of externalism.

I'm kind of inclined to think this is a stand-off - so, for dialectical purposes, reason 2 isn't much good as a motivation for the view in question either.

In the context of quantum fission there are further considerations. I think thought about the future after our own deaths tells against using the co-located persons view in Everettian QM. Have a look at my Phil Quarterly paper from earlier this year if you're interested - it's called 'Macroscopic ontology in Everettian Quantum Mechanics' (Had to remove the link as your comment system thought it was spam). The positive proposal in that paper would tend to undermine reason 3, at least in the quantum case, as well, by providing an alternative grounding for Everettian confirmation theory.

Cheers

Alastair

Wolfgang Schwarz

Pre-fission possibilities

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