Reading Yudkowsky, part 46

by Luke Muehlhauser on June 15, 2011 in Eliezer Yudkowsky,Resources,Reviews

AI researcher Eliezer Yudkowsky is something of an expert at human rationality, and at teaching it to others. His hundreds of posts at Less Wrong are a treasure trove for those who want to improve their own rationality. As such, I’m reading all of them, chronologically.

I suspect some of my readers want to “level up” their rationality, too. So I’m keeping a diary of my Yudkowsky reading. Feel free to follow along.

His 384th post is Causality and Moral Responsibility:

Let’s say that John is standing in front of an orphanage which is on fire, but not quite an inferno yet; trying to decide whether to run in and grab a baby or two.  Let us suppose two slightly different versions of John – slightly different initial conditions.  They both agonize.  They both are torn between fear and duty.  Both are tempted to run, and know how guilty they would feel, for the rest of their lives, if they ran.  Both feel the call to save the children.  And finally, in the end, John-1 runs away, and John-2 runs in and grabs a toddler, getting out moments before the flames consume the entranceway.

This, it seems to me, is the very essence of moral responsibility – in the one case, for a cowardly choice; in the other case, for a heroic one.  And I don’t see what difference it makes, if John’s decision was physically deterministic given his initial conditions, or if John’s decision was preplanned by some alien creator that built him out of carbon atoms, or even if – worst of all – there exists some set of understandable psychological factors that were the very substance of John and caused his decision.

And as for there being psychological factors that determine your decision – well, you’ve got to be something, and you’re too big to be an atom.  If you’re going to talk about moral responsibility at all – and I do regard myself as responsible, when I confront my dilemmas – then you’ve got to be able to be something, and that-which-is-youmust be able to do something that comes to a decision, while still being morally responsible.

Just like a calculator is adding, even though it adds deterministically, and even though it was designed to add, and even though it is made of quarks rather than tiny digits.

Next, Possibility and Couldness:

…let’s talk about this notion of “possibility”.  I can tell, to some degree, whether a world is actual or not actual; what does it mean for a word to be “possible”?

I know what it means for there to be “three” apples on a table.  I can verify that experimentally, I know what state of the world corresponds it.  What does it mean to say that there “could” have been four apples, or “could not” have been four apples?  Can you tell me what state of the world corresponds to that, and how to verify it?  Can you do it without saying “could” or “possible”?

I know what it means for you to rescue a toddler from the orphanage.  What does it mean for you to could-have-not done it?  Can you describe the corresponding state of the world without “could”, “possible”, “choose”, “free”, “will”, “decide”, “can”, “able”, or “alternative”?

The answer:

You could eat the banana, if you wanted.  And you could jump off a cliff, if you wanted.  These statements are both true, though you are rather more likely to want one than the other.

You could even flatly say, “I could jump off a cliff” and regard this as true - if you construe could-ness according to reachability, and count actions as primitively reachable.  But this does not challenge deterministic physics; you will either end up wanting to jump, or not wanting to jump.

The statement, “I could jump off the cliff, if I chose to” is entirely compatible with “It is physically impossible that I will jump off that cliff”.  It need only be physically impossible for you to choose to jump off a cliff – not physically impossible for any simple reason, perhaps, just a complex fact about what your brain will and will not choose.

What is required for free will? Many people think it is that you must be The Ultimate Source of your decisions:

Faced with a burning orphanage, you ponder your next action for long agonizing moments, uncertain of what you will do.  Finally, the thought of a burning child overcomes your fear of fire, and you run into the building and haul out a toddler.

There’s a strain of philosophy which says that this scenario is not sufficient for what they call “free will”.  It’s not enough for your thoughts, your agonizing, your fear and your empathy, to finally give rise to a judgment.  It’s not enough to be the source of your decisions.

No, you have to be the ultimate source of your decisions.  If anything else in your past, such as the initial condition of your brain, fully determined your decision, then clearly you did not.

Are you the true source of your decision to run into the burning orphanage?  What if your parents once told you that it was right for people to help one another?  What if it were the case that, if your parents hadn’t told you so, youwouldn’t have run into the burning orphanage?  Doesn’t that mean that your parents made the decision for you to run into the burning orphanage, rather than you?

On several grounds, no:

If it were counterfactually the case that your parents hadn’t raised you to be good, then it would counterfactually be the case that a different person would stand in front of the burning orphanage.  It would be a different person who arrived at a different decision.  And how can you be anyone other than yourself? Your parents may have helped pluck you out of Platonic person-space to stand in front of the orphanage, but is that the same as controlling the decision of your point in Platonic person-space?

Or:  If we imagine that your parents had raised you differently, and yet somehow, exactly the same brain had ended up standing in front of the orphanage, then the same action would have resulted.  Your present self and brain, screens off the influence of your parents – this is true even if the past fully determines the future.

But above all:  There is no single true cause of an event.  Causality proceeds in directed acyclic networks.  I see no good way, within the modern understanding of causality, to translate the idea that an event must have a singlecause.  Every asteroid large enough to reach Earth’s surface could have prevented the assassination of John F. Kennedy, if it had been in the right place to strike Lee Harvey Oswald.  There can be any number of prior events, which if they had counterfactually occurred differently, would have changed the present.  After spending even a small amount of time working with the directed acyclic graphs of causality, the idea that a decision can only have a single true source, sounds just plain odd.

So there is no contradiction between “My decision caused me to run into the burning orphanage”, “My upbringing caused me to run into the burning orphanage”, “Natural selection built me in such fashion that I ran into the burning orphanage”, and so on.  Events have long causal histories, not single true causes.

Next is a discussion of Passing the Recursive Buck. Grasping Slippery Things analyzes the train of thought that may occur when trying to get your head around difficult concepts. Ghosts in the Machine rejects, obviously, the notion of a ghost in the (AI) machine. LA-602 vs. RHIC is an examination of rigorous attempts to estimate existential risk.

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{ 9 comments… read them below or add one }

Rufus June 15, 2011 at 6:44 pm

It seems to me that EY is merely asserting that there is no problem between determinism and moral responsibility simply because both must be the case. But this is to ignore the philosophical issues at the heart of the matter. There are a couple of issues that seem fairly apparent to me: 1) ought implies can, 2) there is no adequate account of personhood given determinism and physicalism.

The first problem is fairly well known. Since John cannot do otherwise, there is no real sense in which he ought to do it. We might “feel” that he ought to do x. He might feel that he ought to do x. Those feelings might even play a causal role in determining whether he will do x. Saying that John “ought to do x” or is “morally responsible for x” is really just a sloppy way of expressing a wish about the outcome of an extremely complex causal nexus. If EY says “John ought to rescue the orphan”, EY is merely cheering the idea that the causal nexus might workout in that fashion. He might even try to influence events to bring this about, but of course, EY’s cheers or jeers are also causally determined. Why must determinists insist that there is such thing as moral responsibility. It seems that they are determined not to follow their presuppositions to their logical conclusions.

The second point is that moral responsibility requires that there exists persons who are morally responsible. I see no reason, given physicalism and determinism, to think there is such a thing as a “point in Platonic person-space” that corresponds to a person. What is this point? Is it a particular quark, string, or photon?

This reminds me of Epicharmus’ paradox:

A man is approaching for payment of his portion of a fee for a forthcoming banquet. Lacking money, he resorts to a riddle: If you have a number of pebbles and add a pebble or subtract a pebble, do you have the same number of pebbles? No, replies the creditor. Or again, if you have a length of one cubit and add or subtract a bit, then would that length still exist? No, replies the creditor. The debtor then invites the creditor to think of men the same way. Men are always changing, some growing, some diminishing. Since this applies both to the creditor and the debtor, neither of them is the same as they were yesterday or the same as they will be in the future. The creditor acquiesces to this philosophical point. The debtor then triumphantly concludes that he owes nothing. After all, he is no the one who contracted to pay the fee. That man is gone. Nor will he be the one enjoying the banquet. That man is yet to be. The creditor does not know what to say. Finally he strikes the debtor. Reeling from the blow, the debtor angrily protests the assault. The creditor expresses sympathy but explains that he is not the man who stuck him. (A Brief History of the Paradox, R. Sorensen 2003, 130-131).

So given the Heraclitean flux of quantum physics, and the presupposition that only physical things exist, what metaphysical account for persons could there be? No persons, no moral responsibility — just buzzing little particles determined and determining one another.

Thanks,

Rufus

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PDH June 16, 2011 at 7:17 am

Rufus, Eliezer has written extensively on this subject, so you should at least familiarise yourself with his thoughts on the matter before commenting. Check out the rest of the sequence on Quantum Physics, particularly the following articles:

http://lesswrong.com/lw/pm/identity_isnt_in_specific_atoms/
http://lesswrong.com/lw/po/three_dialogues_on_identity/
http://lesswrong.com/lw/pl/no_individual_particles/
http://lesswrong.com/lw/qx/timeless_identity/

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Rufus June 16, 2011 at 6:36 pm

PDH,

Rufus, Eliezer has written extensively on this subject, so you should at least familiarise yourself with his thoughts on the matter before commenting. Check out the rest of the sequence on Quantum Physics, particularly the following articles:

Thanks for the links. I went through them today and did not find any explanation for personal identity, perhaps I missed the point you were trying to highlight for me.

What I found is that EY affirms a particular interpretation of quantum mechanics and asserts it as descriptive of reality. I am no expert on quantum mechanics, but I am wary of such moves. I am aware that there are currently competing theories of how we ought to understand the ontological implications of quantum mechanics, and EY’s analogies and thought experiments do little to settle the matter for me. Frankly, I think it should do little to compel the assent of anyone’s judgment. At best, it is an interesting interpretation or endorsement of an interpretation offered by a non-expert with a philosophical axe to grind, i.e. he wants to make the case that cryonics and “uploading” are no more problematic that simply existing in this quantum reality. I would bet, without having the evidence, that if you asked a professional quantum physicists what the ontological implicates of quantum mechanics were, they would admit that they haven’t the foggiest. They would tell us that the equations work and that they are extraordinarily accurate for predicting outcomes in experiments. I would guess that they would say that any move beyond that risks confusing models and equations for reality (a very common fallacy in science, I bet EY has even come up with his own name for this fallacy).

BUT… assuming EY is correct in his interpretation, I did not see an argument for personal identity whatsoever. What I read was an argument against the numerical individuation of “a blob of amplitude in field configuration space” (gotta love “Yudkowskese”). If anything, this makes the project of understanding identity and individuation even more problematic. Perhaps I missed the part where EY said what it was that grounded an individual personal identity. Rather, it seems that he is saying that we can configure amplitudes such that the resulting “entity” “affirms” continuity and individuation over time. In general, then, I think EY ought to agree with my comments regarding the illusion of personal identity. To speak of personal identity is to enter into a fictional language game having assumed certain things about reality which simply are not the case. But then moral responsibility is also just a logical fiction, following upon false premises about identity and individuation. Why can’t physicalists simply follow the argument to where it logically leads them?

I am thick-headed and perhaps a little dull PDH, please spell out EY’s argument for personal identity in language that someone like me can understand. I do not have the time to click through thousands of hyperlinks to figure out what all of these neologisms mean. In all honesty, I really want to know the answer being offered here. I don’t pretend to think personal identity is a problem unique to physicalism, but I think it is obviously problematic for the very reasons EY points out.

Best,

Rufus

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PDH June 16, 2011 at 7:34 pm

Rufus, the idea of identical particles is not unique to a particular interpretation of QM. Check the Wiki:

http://en.wikipedia.org/wiki/Identical_particles

No doubt EY would agree that your conception of identity is naive but it doesn’t follow that no account of personal identity can be given. The whole of Timeless Identity is such an account. Is there something specific you don’t understand?

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Rufus June 16, 2011 at 9:13 pm

PDH,

I was speaking more generally about the metaphysical/ontological and even logical implications of quantum mechanics. These are live debates being discussed by physicists and philosophers of science. The philosopher Steven French writes the following in a very helpful SEP article:

We now appear to have an interesting situation. Quantum mechanics is compatible with two distinct metaphysical ‘packages’, one in which the particles are regarded as individuals and one in which they are not. Thus, we have a form of ‘underdetermination’ of the metaphysics by the physics (see van Fraassen 1985 and 1991; French 1989a; Huggett 1997). This has implications for the broader issue of realism within the philosophy of science. If asked to spell out her beliefs, the realist will point to currently accepted fundamental physics, such as quantum mechanics, and insist that the world is, at least approximately, however the physics says it is. Of course, there are the well-known problems of ontological change (giving rise to the so-called pessimistic meta-induction) and underdetermination of theories by the data. However, the above underdetermination of metaphysical packages seems to pose an even more fundamental problem, as the physics involved is well entrenched and the difference in the metaphysics seemingly as wide as it could be. These packages support dramatically different world-views: one in which quantal particles are individuals and one in which they are not. The realist must then face the question: which package corresponds to the world? The physics itself can offer no help whatsoever and any justification for choosing one package over the other which appeals to metaphysical considerations, for example, runs the risk of drastically watering down the science in scientific realism.

Faced with this situation, the anti-realist may conclude ‘so much for metaphysics’ and insist that all that theories can tell us is how the world could be (van Fraassen 1991). A possible alternative would be for realism to retreat from a metaphysics of objects entirely and develop an ontology of structure compatible with the physics (Ladyman 1998 and 2009). An early attempt to do this in the quantum context can be seen in the work of Cassirer who noted the implications for our notion of individual objects and concluded that particles were describable only as ‘“points of intersection” of certain relations’ (1937, p. 180) Setting aside the neo-Kantian elements in Cassirer’s structuralism, the articulation of this view of quantum entities remains a matter of considerable debate (Ladyman and Ross 2007; French and Ladyman 2011). (French 2011, Identity and Individuality in Quantum Theory).

It seems to me that the metaphysical questions are still being worked out (realists v. anti-realists, etc.). I don’t think there is anything close to a consensus as of right now on what the exact implication of the “identity of particles” holds for our conception of reality. But I argue that if you hold “quantum amplitude blobs” to be the most basic or fundamental components of reality, as I take EY to be doing, then I see no case for the reality of persons. If there are no persons, then nothing exists to which morality can be ascribed.

No doubt EY would think that my conception of identity is naive — this much we agree upon. Perhaps some account of personal identity can be given, but I am simply not seeing it from what he has written. But you have asked for something specific that I do not understand, so here we go. This is from “Timeless Identity”:

But on an ontologically fundamental level, nothing with a persistent identity moves through time.

Even the braid itself is not ontologically fundamental; a human brain is a factor of a larger wavefunction that happens to factorize.

Then what is preserved from one time to another? On an ontologically basic level, absolutely nothing.

But you will recall that I earlier talked about any perturbation which does not disturb your internal narrative, almost certainly not being able to disturb whatever is the true cause of your saying “I think therefore I am” – this is why you can’t leave a person physically unaltered, and subtract their consciousness. When you look at a person on the level of organization of neurons firing, anything which does not disturb, or only infinitesimally disturbs, the pattern of neurons firing – such as flipping a switch from across the room – ought not to disturb your consciousness, or your personal identity.

If you were to describe the brain on the level of neurons and synapses, then this description of the factor of the wavefunction that is your brain, would have a very great deal in common, across different cross-sections of the braid. The pattern of synapses would be “almost the same” – that is, the description would come out almost the same – even though, on an ontologically basic level, nothing that exists fundamentally is held in common between them. The internal narrative goes on, and you can see it within the vastly higher-level view of the firing patterns in the connection of synapses. The computational pattern computes, “I think therefore I am”. The narrative says, today and tomorrow, “I am Eliezer Yudkowsky, I am a rationalist, and I have something to protect.” Even though, in the river that never flows, not a single drop of water is shared between one time and another.

If there’s any basis whatsoever to this notion of “continuity of consciousness” – I haven’t quite given up on it yet, because I don’t have anything better to cling to – then I would guess that this is how it works.

Now this seems to suggest that EY holds to the continuity of consciousness simply because he has nothing better to cling to… this despite the fact that he says that on the ontologically fundamental level, nothing is the same over time. Am I misunderstanding EY? It seems as though he is saying that an entity E1 could say “I am EY” and that another entity E2, with “almost the same” pattern might say “I am the same EY as E1″. But this is merely to say that brains that are nearly the same tend to think they are the same even though, at the most basic ontological level, they are not the same. The brain is duped into ascribing personal identity in the way it is duped into thinking a tree or football is a unified self-same object over time.

Why not cling to the idea that there clearly is no individuation for that which is ontologically basic, nor for entities over time. Personal identity is a mere illusion. He “clings” to this belief, but I see no reason for why he should, except that he has not given up (hope) that he will figure a way to salvage this important idea of continuity (because if he can’t there are obvious untoward consequences for his world-view). I am not seeing an account of personal identity here, I am seeing a hope and a prayer that his account of similar enough brain patters is sufficient to ground continuity while denying continuity all together at the most fundamental ontological level.

-Rufus

P.S. Apologies to you and to Luke for the length of my comments here. I suppose if this conversation carries on too long we could take it off site so as to not disturb the readership with my blabbering on about identity and individuation. If you think that would be appropriate and would like to continue this discussion, please let me know.

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PDH June 17, 2011 at 8:01 am

Rufus, on the issue of scientific realism, Less Wrongian Bayesians are looking for the most plausible available interpretation. It’s about accuracy. The analogy used most commonly is that of the map and the territory. We don’t have direct epistemic access to the territory, we have to make inferences, some of which will be better than others. They also continue Popper’s tradition of distinguishing between epistemology and philosophy of science. Falsifiability, for example, is a criterion that helps us distinguish between science and non-science but not always between truth and non-truth. I don’t have time to submit my hypothesis that a car is about to run me over to a peer reviewed journal, nonetheless it might be rational for me to get out of the way.

Thus, a Less Wrongian might hold both that, say, the MWI of QM is by far the most plausible explanation and hold it to be true whilst acknowledging that mainstream science would not be so bold. If new evidence comes along that confirms one hypothesis over another they would simply update their probability distributions accordingly.

You’re going to hate me for this but there is another article on this topic you might want to read (which is pretty much guaranteed to invite further controversy into this discussion, but whatever):

http://lesswrong.com/lw/ph/can_you_prove_two_particles_are_identical/

On the issue of identity, if I take an mp3 of The Song Remains the Same and copy it to an mp3 player, then on one view of identity its title will still be essentially correct. On another view one will be ‘the original’ and another just a copy. Though whether the original song is the original mp3, the original recording, the original performance or something else is not clear to me.

(Complicating things a little is the fact that the pattern of information that constitutes my identity changes over time as I have new experiences. Make an exact copy of me in Australia and the Australian PDH will be a continuation of my story just as much as the PDH sitting at this computer, and neither of them will be made of the same atoms. But almost immediately their experiences will diverge. One will probably be a lot warmer, for starters.

However, even in a classical universe you are not the same person from one moment to the next. You have new memories, new thoughts, new feelings etc. If you regard that as a continuation of your identity then Yudkowsky’s ontology presents no new problems.)

So we have two distinct conceptions of identity here. One is indeed problematic, the other seems fine to me. If you don’t consider the latter to be real identity then we are in agreement that there is no such thing as identity and this entire debate is just a dispute over which words to use. In any case, there are no interesting empirical consequences of this. It won’t – and shouldn’t – affect anyone’s behaviour in the slightest.

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Rufus June 17, 2011 at 3:28 pm

PDH,

We don’t have direct epistemic access to the territory, we have to make inferences, some of which will be better than others. They also continue Popper’s tradition of distinguishing between epistemology and philosophy of science. Falsifiability, for example, is a criterion that helps us distinguish between science and non-science but not always between truth and non-truth. I don’t have time to submit my hypothesis that a car is about to run me over to a peer reviewed journal, nonetheless it might be rational for me to get out of the way.

Thus, a Less Wrongian might hold both that, say, the MWI of QM is by far the most plausible explanation and hold it to be true whilst acknowledging that mainstream science would not be so bold. If new evidence comes along that confirms one hypothesis over another they would simply update their probability distributions accordingly.

These comments remind me of William James’ Will to Believe. When a car is about to hit you, belief that the car will cause you harm is living, forced, and momentous. Thus, you cannot withhold judgment about the hypothesis that the car will cause you harm, you have to act. James contrasts such options with ones which can be put off until the data is in. His examples come from science. The chemist can test the hypothesis without assenting to any position on the matter until the evidence is in. So perhaps the “Less-Wrongian” is justified in assenting to belief in the MWI interpretation of QM before the scientist would do so. However, I see no reason to think that the option of this interpretation is far more pressing for the “Less Wrongian” than it is for the scientist. What urgency is compelling this belief? What is the “car” that you are trying to avoid? Shouldn’t we also assess the significance of assenting to this belief if that belief turns out to be wrong? For instance, suppose you advocate a reallocation of charitable donation so as to develop “futurist” technologies that you assume will advance humanity, but only if the MWI happens to be true. By rushing into the belief more boldly than the scientist, your advocacy might end up causing a great deal of harm. Wouldn’t it be more prudent to try to avoid error in this case, than to race after the truth?

It seems to me that our discussion has broken into two: 1) whether EY or Less-Wrongians are justified in believing a certain interpretation of QM, and 2) whether that interpretation is capable of providing a coherent account of continuous personal identity. To the first point I am somewhat open, perhaps the weight of evidence favors the current interpretation. I am skeptical of the metaphysical/ontological interpretation of QM (because I think mathematics requires something like a principle of identity, which such interpretations presume to violate), but my worries may be ill founded here.

So we have two distinct conceptions of identity here. One is indeed problematic, the other seems fine to me. If you don’t consider the latter to be real identity then we are in agreement that there is no such thing as identity and this entire debate is just a dispute over which words to use. In any case, there are no interesting empirical consequences of this. It won’t – and shouldn’t – affect anyone’s behaviour in the slightest.

Yes, this is much like the incompatiblist/compatibilist debate. Incompatibilists require that one be the originating or ultimate cause of an action for that action to be free. Compatibilists define freedom as the ability to act voluntarily. The incompatibilist argues that this is not really freedom, while the compatibilist says its the only “kind” of freedom we can have.

Here we are arguing about identity. You seem to be acknowledging the problems that I point out. I agree that the problems are not unique to quantum mechanics, or physicalism. However, I think that quantum mechanics combined with physicalism offers us no hope of finding that stable “entity” which could ground identity. As a supernaturalist, I am not limited to the empirical flux before us and while personal identity is problematic for my world-view too, I think there are potential answers in immaterial entities like “soul” and “spirit” which may be worked out.

I would say that physicalism, given a classical universe, fails to provide an account of identity. My contention, then, is that there are interesting consequences to the belief that there is no continuity of persons, or personal identity, namely that there is no ontological basis for my belief that I am a unity of consciousness. To me, this means that there is no ultimate justification for moral responsibility. I also maintain that this introduces deep problems into epistemology. Namely, can one possess knowledge, if there is no ontological basis for personal identity.

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hf June 28, 2011 at 1:38 pm

@Rufus: First, thank you for saying that you don’t have the answer either. I naturally disagree that supernaturalism has potential answers “which may be worked out.” Not only have we given theologians a long time to do this with no apparent results, but also it seems unclear what “immaterial entities” could even mean if “material” can include something that acts like mathematical arrows attached to large sets of numbers.

Second, you understandably see Eliezer’s post as a discussion of personal identity. But it also refers to time.

This does not seem on the surface like a problem for a Christian view (nor Jewish, nor Platonist, nor I assume Islamic). All these deities supposedly exist outside of time. So at first it seems quite reasonable within these views to say that time does not fundamentally exist. But it does mean if we try to explain the phenomena by saying that God did it, we would still have to say that time comes from non-time.

Yet our usual understanding of ourselves and our choices requires time in order to make sense. It sounds like you would balk at saying that in the car example, “belief that the car will cause you harm” is an illusion simply because nothing travels from one “time” to another. You’d probably object to saying that either the current Rufus will cease to exist when the moment ends (before the car hits “you”), or “Rufus” exists outside of the illusion of time, and in either case it makes no difference if you jump or not. Probably you want to say that our understanding of causality has some connection to the real world, even if the fate of ‘future Rufus’ does not directly depend on your choices in the present but rather on some feature of reality that exists outside time. This appears to mean that you would have to use Eliezer’s account, or some other way of viewing the passage of time as real without calling it fundamental. I don’t see why we couldn’t do this with personal identity.

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Rufus June 30, 2011 at 6:44 pm

hf,

It seems to me that you are committing some sort of equivocation when you write that “God did it” implies that “time comes from non-time”. The theist would say that time is caused by a non-temporal entity, not by non-time (whatever that might be). Aside from being mind-boggling in a general sense, I do not take this to be logically incoherent. I am a little fuzzy on how this might relate to my issues with personal identity and individuation on physicalism though. I am not really interested in trying to defend some sort of cosmological argument here. My point is more that physicalism not only cannot offer an account for personal identity and individuation, but is radically antithetical to any account being developed (precisely because it is so reductive in stipulating what exists). As a supernaturalist, I am open to the possibility that my personal identity is grounded in some “non-material X” and that this non-material X is the self-same over time, mutible, and accounts for the unity of my conscious experience. Call it the soul, call it mental substance, call it the ding an sich, you could call it “banana” for all I care. As an aside, I am not sure what your mathematical arrows objection amounts to. By immaterial, I simply mean something not composed of matter/energy.

If physicalism were true, then it would not even be the case that there would be a Rufus @ t=0 non-identical to Rufus @ t=1. It is far more radical than that. When I use the word “Rufus” or “I”, I am giving a certain sense from within a common-sense every-day language game that assumes personal identity (perhaps naively). The referent “Rufus” as it is used in everyday language has the sense of “this person who is currently writing on CSA and responding to hf”. If physicalism is true, the referent “Rufus” might remain the same, but the sense is altered. “Rufus” now has the sense of a loose connection of causally related related fundamental/virtual particles. The physicalist pretends that there is no problem of identity because language allows for a shift in sense to go unacknowledged while the referents all remain the same. PDH essentially admitted as much when responding to me. Hence PDH wrote:

So we have two distinct conceptions of identity here. One is indeed problematic, the other seems fine to me. If you don’t consider the latter to be real identity then we are in agreement that there is no such thing as identity and this entire debate is just a dispute over which words to use. In any case, there are no interesting empirical consequences of this. It won’t – and shouldn’t – affect anyone’s behaviour in the slightest.

PDH seems only concerned with the empirical consequences of such a shift in sense, but this because PDH assumes a world-view in which empirical consequences would be the only consequences of importance. That is precisely what is at issue and so it is question-begging to appeal to this as evidence that my point is trivial. Perhaps there would not be empirical consequences if physicalism were “known” to be true, but there would also be metaphysical, moral, and epistemological consequences. I am not even sure if it is the case that there would be no empirical consequences. There are philosophers, I can’t recall names right now, who argue that determinism is true, but the public should not be made aware of this fact. The idea is that if everyone thought determinism were true, it would alter the way people behave in a negative way. The same might be said of physicalism (which typically assumes some form of determinism).

As for your question about time, I cannot provide you with an adequate answer. You are using it as an example to distinguish “real” from “fundamental” and I am afraid the point is lost on me. I do think simples could be self-same over time. Composites, like “Rufus”, are just a convenient short-hand to refer to an arbitrary grouping of certain simples. The problem is, of course, it is convenient short hand for whom? Not for “Rufus” — a mere collection of things.

The problem with non-physicalists talking to physicalists about personal identity is that neither party bothers to get clear on the senses of the terms they use. If a physicalist were to actually use language in a way that reflected the sense (Sinn) of his or her beliefs, the absurdity of the position would quickly manifest. The physicalist must exploit language by hiding behind referents. They continue to use “I” and “you” and “they” when such terms have an entirely different sense within the language.

That is the best I can do to explain my position on the matter. I hope it is food for thought. I hope you don’t disappear into a cloud of simples!

Best,

Rufus

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