A Seldom Considered Argument for Dualism

[Kenny]

(NB: I was asked by someone to post this months ago. I am finally putting it up with the proviso that I am still busy and that responses on my part may be slow in coming)

There is a seldom considered, but to my mind, persuasive argument for dualism, one that focuses on issues of personal identity and the metaphysics of material objects rather than issues in the philosophy of mind. In the contemporary scene, it originates with Roderick Chisholm. An extremely detailed version of it is presented by Dean Zimmerman in the Oxford Handbook of Metaphysics.

Disclaimer: Although I find the argument below persuasive, I realize (and I know this by experience) that it is the sort of argument that often requires living with the issues it raises for a while in order to see its force.

I’ve debated with myself about how to present this argument. I could go for an extremely long, detailed presentation that tries to address the main lines of response that can be given to the argument (and risk losing people), or I could go for an extremely simple presentation that glosses over all that (and risk being justly accused of oversimplifying). I’ve opted for the latter. Let the complications come out in discussion.

So, here it is:

First, a definition:

Let’s say that x “strictly survives” some occurrence if x exists before that occurrence and x exists after that occurrence.

Now, the argument:

(P1) If human persons are material objects, human persons can strictly survive the loss of some of their parts.
(P2) No material object can strictly survive the loss of some it its parts.
(C)Therefore, human persons are not material objects.

I won’t have a lot to say in defense of the first premise. If you can live with its denial, more power to you. I only ask that you sincerely reflect on what its denial commits you to and ask yourself if you can take it seriously. If you can live with its denial (after having sincerely reflected on it and wholeheartedly endorsed it) without being filled with terror at the prospect of getting a haircut or filing your nails, more power to you.

P2, to my mind, is the premise that materialists about human persons should reject. But there is a powerful argument for the truth of P2. Here it goes:

Consider your body. Name it “Body”. Consider the part of Body that consists of all of Body except your left pinky. Call that part “Body-minus”. At time t0, let’s say, Body is intact; it includes your left pinky as a part. Suppose that at t1, however, your left pinky is annihilated. Call the pinkyless, human-body-shaped, material object that remains in your vicinity after this unfortunate event “Deformed”. Note that the following argument appears to be sound:

(1) At t1, Body-minus still exists (because nothing happened to Body-minus except that something external to it was detached from it).

(2) At t1, if Body still exists, Body is identical to Deformed [What else could Body be at that time?].

(3) At t1, if Body-minus still exists, Body-minus is identical to Deformed [What else could Body-minus be then?].

(4) At t1, Body-minus is identical to Deformed [This follows from 1 and 3].

(5) At t1, if Body still exists, Body is identical to Body-minus [This follows from 2, 4 and the fact that identity is an equivalence relation].

(6) At t1, it is not the case that Body is identical to Body-minus [Note, for example, that at t1 if Body and Body-minus both exist, they have different historical properties – Body-minus used to be a proper part of Body, for example, but Body was never a proper part of Body].

(7) Therefore, at t1 it is not the case that Body still exists [5,6].

Of course, a parallel argument could be given with respect to any material body that is said to have survived the loss of a part. So, if the above argument is sound, P2 is true. I think that the above argument is sound.

Well, there it is, an argument for the conclusion that human persons are not material objects. I take it that if human persons are not material objects, substance dualism is true (someone may want to challenge that presumption – if so, go right ahead, and I’ll respond) and I take the argument offered for that conclusion above to be sound. I conclude, therefore, that dualism is true.

[shunyadragon]

Basically I do not like this argument, but I will wait to comment more than a few questions, and follow others who post that have more insight to observe.

What would you say to the simple assumption that . . . 'By the evidence all parts of the individual are physical?'

'Why could an individual not survive without some of it's parts?

[Kenny]

What would you say to the simple assumption that . . . 'By the evidence all parts of the individual are physical?'

I'd say it's false.

'Why could an individual not survive without some of it's parts?

I gave you an argument for that conclusion.

[Kenny]

(P2) No material object can strictly survive the loss of some it its parts.

That should be: (P2) No material object can strictly survive the loss of some of its parts.

[Epoetker]

Mind-body dualism is only the beginning of metaphysical reasoning. Living life is less about separating the mind and the body than ensuring that the visions grasped by the mind are eventually embodied outside of the flesh, at which point one may truly judge whether the idea was good or bad.

See: Music, art, applied science and engineering, architecture, the raising of a family under shared tradition, the building of political systems, all good things under heaven. The discipline of morality is only about separating mind from body for a short time so that the mid may dwell on the spiritual things necessary to keep it attuned to the truth.

Given how enmeshed both states of being are, however, such a separated state is rarely something to be maintained for long without ill effects.

Great start of an idea though.

[Kenny]

Mind-body dualism is only the beginning of metaphysical reasoning. Living life is less about separating the mind and the body than ensuring that the visions grasped by the mind are eventually embodied outside of the flesh, at which point one may truly judge whether the idea was good or bad.

The argument in the OP has nothing directly to do with how we should live. It is simply an argument concerning what sort of thing we are.

[JimL]

(NB: I was asked by someone to post this months ago. I am finally putting it up with the proviso that I am still busy and that responses on my part may be slow in coming)

There is a seldom considered, but to my mind, persuasive argument for dualism, one that focuses on issues of personal identity and the metaphysics of material objects rather than issues in the philosophy of mind. In the contemporary scene, it originates with Roderick Chisholm. An extremely detailed version of it is presented by Dean Zimmerman in the Oxford Handbook of Metaphysics.

Disclaimer: Although I find the argument below persuasive, I realize (and I know this by experience) that it is the sort of argument that often requires living with the issues it raises for a while in order to see its force.

I’ve debated with myself about how to present this argument. I could go for an extremely long, detailed presentation that tries to address the main lines of response that can be given to the argument (and risk losing people), or I could go for an extremely simple presentation that glosses over all that (and risk being justly accused of oversimplifying). I’ve opted for the latter. Let the complications come out in discussion.

So, here it is:

First, a definition:

Let’s say that x “strictly survives” some occurrence if x exists before that occurrence and x exists after that occurrence.

Now, the argument:

(P1) If human persons are material objects, human persons can strictly survive the loss of some of their parts.
(P2) No material object can strictly survive the loss of some it its parts.
(C)Therefore, human persons are not material objects.

I won’t have a lot to say in defense of the first premise. If you can live with its denial, more power to you. I only ask that you sincerely reflect on what its denial commits you to and ask yourself if you can take it seriously. If you can live with its denial (after having sincerely reflected on it and wholeheartedly endorsed it) without being filled with terror at the prospect of getting a haircut or filing your nails, more power to you.

P2, to my mind, is the premise that materialists about human persons should reject. But there is a powerful argument for the truth of P2. Here it goes:

Consider your body. Name it “Body”. Consider the part of Body that consists of all of Body except your left pinky. Call that part “Body-minus”. At time t0, let’s say, Body is intact; it includes your left pinky as a part. Suppose that at t1, however, your left pinky is annihilated. Call the pinkyless, human-body-shaped, material object that remains in your vicinity after this unfortunate event “Deformed”. Note that the following argument appears to be sound:

(1) At t1, Body-minus still exists (because nothing happened to Body-minus except that something external to it was detached from it).

(2) At t1, if Body still exists, Body is identical to Deformed [What else could Body be at that time?].

(3) At t1, if Body-minus still exists, Body-minus is identical to Deformed [What else could Body-minus be then?].

(4) At t1, Body-minus is identical to Deformed [This follows from 1 and 3].

(5) At t1, if Body still exists, Body is identical to Body-minus [This follows from 2, 4 and the fact that identity is an equivalence relation].

(6) At t1, it is not the case that Body is identical to Body-minus [Note, for example, that at t1 if Body and Body-minus both exist, they have different historical properties – Body-minus used to be a proper part of Body, for example, but Body was never a proper part of Body].

(7) Therefore, at t1 it is not the case that Body still exists [5,6].

Of course, a parallel argument could be given with respect to any material body that is said to have survived the loss of a part. So, if the above argument is sound, P2 is true. I think that the above argument is sound.

Well, there it is, an argument for the conclusion that human persons are not material objects. I take it that if human persons are not material objects, substance dualism is true (someone may want to challenge that presumption – if so, go right ahead, and I’ll respond) and I take the argument offered for that conclusion above to be sound. I conclude, therefore, that dualism is true.

Not sure if I am understanding your argument, so perhaps this question makes sense and perhaps it doesn't, but how then would you define substance dualism as it relates to the nature of the severed left pinky? Does the pinky itself have a dual nature like the rest of the body from which it was severed.

[Kenny]

Not sure if I am understanding your argument, so perhaps this question makes sense and perhaps it doesn't, but how then would you define substance dualism as it relates to the nature of the severed left pinky? Does the pinky itself have a dual nature like the rest of the body from which it was severed.

As I am using it, the term ‘substance dualism’ refers to the thesis that any given human person is (at least in part) composed or constituted by an immaterial substance (aka a soul) or is identical to one (my own view is that human persons are identical to immaterial substances, but that’s a stronger thesis that substance dualism proper).

Substance dualism is not the thesis that bodies have a “dual nature” (whatever that would mean in this context).

To put it in something closer to lay terms, substance dualism is the thesis that human persons have immaterial souls (that they “have them” either by being identical to them or by being partly composed or constituted by them).

ETA: In this thought experiment, there never is a “severed pinky”. Rather, the pinky gets annihilated (that’s important for certain technical reasons).

[JimL]

As I am using it, the term ‘substance dualism’ refers to the thesis that any given human person is (at least in part) composed or constituted by an immaterial substance (aka a soul) or is identical to one (my own view is that human persons are identical to immaterial substances, but that’s a stronger thesis that substance dualism proper).

Substance dualism is not the thesis that bodies have a “dual nature” (whatever that would mean in this context).

To put it in something closer to lay terms, substance dualism is the thesis that human persons have immaterial souls (that they “have them” either by being identical to them or by being partly composed or constituted by them).

ETA: In this thought experiment, there never is a “severed pinky”. Rather, the pinky gets annihilated (that’s important for certain technical reasons).

And does the immaterial substance or soul which is in, for lack of a better term, the body, exist throughout the body and annihilated with the parts thereof, or in other words, is the fingers soul annihilated along with the material finger, or is the immaterial substance or soul of the body concentrated in only one specific part of the body?

[Kenny]

And does the immaterial substance or soul which is in, for lack of a better term, the body

According to standard dualist views, souls have no spatial location whatsoever. I’m actually attracted (for various philosophical reasons) to the non-standard dualist view that souls do have spatial location. But, as far as this argument is concerned, I needn’t take a position on that subject one way or another.

exist throughout the body and annihilated with the parts thereof

According to standard substance dualist views, souls are mereological simples (i.e. they don’t have any proper parts. NB: A “proper” part of something is a part of that thing that is not identical to it). That’s also my view. But, again, as far as this argument is concerned, one needn’t make any commitment concerning whether souls have parts.
And note that the body-minus argument makes no assumptions about whether your soul strictly survives the annihilation of your pinky in the envisioned scenario (all it aims to show is that your body doesn’t strictly survive). Of course, the dualist would want to maintain that it does. And if she endorses the body-minus argument, she will want to take care to maintain a view of the soul’s relationship to the body which does not entail that the soul strictly survives the annihilation of the pinky only if the body does. But this issue is irrelevant to whether or not the body-minus argument is sound.

or in other words, is the fingers soul annihilated along with the material finger, or is the immaterial substance or soul of the body concentrated in only one specific part of the body?

Well, here’s what I would say (but, as far as I can tell, none of this is actually relevant to the argument). The soul is a mereological simple. It has no proper parts and so it has nothing like a “pinky” (almost all dualists would agree on this point).

Now, either the soul is spatially located in the vicinity of the body or its not (remember that the standard dualist view is that the soul is not spatially located at all). I don’t know which is the case, but I’m sympathetic to the view that the soul is located within the vicinity of the body. If it is located within the vicinity of the body, then either it is spatially extended or it is not (note that if the soul is spatially extended, it is possible for there to be extended mereological simples – whether that’s possible, or even makes sense, is a matter of controversy among philosophers).

If it is not spatially extended but is spatially located, then I suppose the most plausible thing to say is that it is located somewhere in the brain (but who really knows).
If it is spatially extended, I suppose the most plausible thing to say is that it fits in exactly the same spatial region as the body it inhabits does (but again, who really knows). If that’s the case, then when the body it inhabits changes shape or comes to occupy different regions of space, it changes space and occupies different regions of space accordingly. When the body it occupies (strictly speaking, it comes to occupy a different body after the annihilation event) is no longer having-a-left-pinky shaped, the soul (which was, by the current hypothesis, also formally having-a-left-pinky shaped) also comes to be no longer so shaped. But none of this involves its losing any parts (it doesn’t have any proper parts to lose).

In any case, though, I don’t claim to know much about the nature of the soul or about the precise nature of its relationship to the body. I don’t have to claim that in order to claim that I have a sound argument for the conclusion that are souls. So, again, I don’t really see the relevance of these questions.

[ENeGMA]

(NB: I was asked by someone to post this months ago. I am finally putting it up with the proviso that I am still busy and that responses on my part may be slow in coming)

There is a seldom considered, but to my mind, persuasive argument for dualism, one that focuses on issues of personal identity and the metaphysics of material objects rather than issues in the philosophy of mind. In the contemporary scene, it originates with Roderick Chisholm. An extremely detailed version of it is presented by Dean Zimmerman in the Oxford Handbook of Metaphysics.

Disclaimer: Although I find the argument below persuasive, I realize (and I know this by experience) that it is the sort of argument that often requires living with the issues it raises for a while in order to see its force.

I’ve debated with myself about how to present this argument. I could go for an extremely long, detailed presentation that tries to address the main lines of response that can be given to the argument (and risk losing people), or I could go for an extremely simple presentation that glosses over all that (and risk being justly accused of oversimplifying). I’ve opted for the latter. Let the complications come out in discussion.

So, here it is:

First, a definition:

Let’s say that x “strictly survives” some occurrence if x exists before that occurrence and x exists after that occurrence.

Now, the argument:

(P1) If human persons are material objects, human persons can strictly survive the loss of some of their parts.
(P2) No material object can strictly survive the loss of some it its parts.
(C)Therefore, human persons are not material objects.

I won’t have a lot to say in defense of the first premise. If you can live with its denial, more power to you. I only ask that you sincerely reflect on what its denial commits you to and ask yourself if you can take it seriously. If you can live with its denial (after having sincerely reflected on it and wholeheartedly endorsed it) without being filled with terror at the prospect of getting a haircut or filing your nails, more power to you.

Prima facie, this argument doesn't trouble computation theories of mind. If we're implementations of states of an abstract Turing machine, we can survive the loss of some of our parts (just as a computer processor can implement Microsoft Word even though it undergoes physical changes).

And this would vindicate token physicalism which is, by far, the most prevalent form of physicalism about the mind.

Also, this argument is only as strong as assumptions about personal identity. But possibly the metaphysics of mind and personal identity have little to do with each other since personal identity is unimportant or indeterminate, in the Parfitian sense. If that were the case, no certain metaphysical conclusions could rest on highly dubious premises about personal identity.

P2, to my mind, is the premise that materialists about human persons should reject. But there is a powerful argument for the truth of P2. Here it goes:

Consider your body. Name it “Body”. Consider the part of Body that consists of all of Body except your left pinky. Call that part “Body-minus”.

Already it's tendentious whether any proper subset of an objects parts is itself an object. Why should I believe that there can be an object such as body-minus that's (roughly) coincident with my body? It of course follows trivially that there are countless such objects. This is deeply implausible. If I'm conscious, then body-minus is conscious. So it follows that there are innumerable conscious objects that aren't identical with me but are varyingly co-extensive with me.

And if I accept that, it seems I can help myself to a sort of counterpart relation between "body-parts" such that personal identity holds if enough of my "body-parts" exist. Personal identity, on this picture, becomes indeterminate and partial, since, strictly speaking, I can't survive the loss of any of my parts. But closely related physical objects will still exist, and if personal identity consists in *that* then a materialist picture could be maintained.

And so, I maintain, any materalist about mind who accepted Zimmerman's metaphysics would have a view of personal identity on which personal identity was always partial and indeterminate and consisted in certain relations between distinct physical objects. I'm sure you can imagine, in outline, how such a theory might go whether or not you find it plausible.

At time t0, let’s say, Body is intact; it includes your left pinky as a part. Suppose that at t1, however, your left pinky is annihilated. Call the pinkyless, human-body-shaped, material object that remains in your vicinity after this unfortunate event “Deformed”. Note that the following argument appears to be sound:

(1) At t1, Body-minus still exists (because nothing happened to Body-minus except that something external to it was detached from it).

I don't know if I accept this. What is body-minus? Just a collection of parts? Well, if it loses the external pinky, it's going to lose some blood, and since blood cells are proper parts of body-minus, body-minus no longer exists.

Arguably body-minus stopped existing the very next instant, as some of its blood cells left body-minus and moved into attached but unrelated pinky next to it. If body can't survive the loss of one of its parts, body-minus can't survive the loss of one of its.

(2) At t1, if Body still exists, Body is identical to Deformed [What else could Body be at that time?].

(3) At t1, if Body-minus still exists, Body-minus is identical to Deformed [What else could Body-minus be then?].

(4) At t1, Body-minus is identical to Deformed [This follows from 1 and 3].

Body-minus doesn't exist anymore, it seems. Some parts of body-minus are gone. You could try to define body-minus* as that object which has all of the parts of body except those lost when the pinky is annihilated, but then this would make body-minus* not identical with Deformed, as Deformed will have some blood that was in Pinky but wasn't in body-minus*.

I sure hope that you the reason you're preferring annihilation to detachment is just forestall this objection, because that would be monstrously ad hoc for all kinds of reasons. For example, if you think annihilation if metaphysically possible you have to think something coming into exist ex nihilo is metaphysically possible. If it turns out that this argument crucially rests on this being annihilation, with some additional ad hoc features (like no bleeding), then this an extraordinarily weak argument.

(5) At t1, if Body still exists, Body is identical to Body-minus [This follows from 2, 4 and the fact that identity is an equivalence relation].

(6) At t1, it is not the case that Body is identical to Body-minus [Note, for example, that at t1 if Body and Body-minus both exist, they have different historical properties – Body-minus used to be a proper part of Body, for example, but Body was never a proper part of Body].

(7) Therefore, at t1 it is not the case that Body still exists [5,6].

Of course, a parallel argument could be given with respect to any material body that is said to have survived the loss of a part. So, if the above argument is sound, P2 is true. I think that the above argument is sound.

Well, there it is, an argument for the conclusion that human persons are not material objects. I take it that if human persons are not material objects, substance dualism is true (someone may want to challenge that presumption – if so, go right ahead, and I’ll respond) and I take the argument offered for that conclusion above to be sound. I conclude, therefore, that dualism is true.

First of all, it can't be ignored that this is a radically counter-intuitive metaphysics. It entails that no physical objects survive the loss of even a single atom, which means that no physical object has persistance conditions across change.

And since the argument generalizes, it's solution generalizes. Whatever we want to say against the argument that an object losing a part is a different object we can say in this particular instance. This is a hotly contested issue in metaphysics, and I must admit to not being very knowledgable about it. But I think we should do all that we can to avoid the conclusion that no physical objects persist through a change in their parts. If there's even a plausible way of avoiding this conclusion, I think we should we should take it and run with it, because this is all but compositional nihilism.

Intuitively, the solution is to make a human being identical to something less brittle than the particular set of parts which happen to make it up (this argument works if even a single atom is lost, for instance, which should give us a clue as to where the problem lies). What this argument takes the materialist position to be is that a human person is identical to a certain set of atoms arranged a certain way, such that the loss of even a single atom would shatter the object. Why the materialist is committed to this absurd claim is unclear to me.

In general, what I want to say is that a conclusion is only as good as its premises. And the premises here include doubtful claims about personal identity (i.e. that there is such a thing, contra Parfit) and the metaphysics of material objects. This coupled with all of the powerful arguments we have against substance dualism makes this argument seem rather weak to me. Even if there were nothing I could say in response to this argument as presented, I would still find it far more plausible to take refuge in doubts about the determinacy of personal identity than I would to accept this conclusion.

I just really don't see this is a very compelling argument at all.

[Kenny]

Prima facie, this argument doesn't trouble computation theories of mind. If we're implementations of states of an abstract Turing machine

I’m pretty sure that whatever we are, we’re not those. Maybe our mental states are those, but I’m talking about us, not about our mental states. As I said in the OP, this argument doesn’t have much to do with issues in phil mind. It comes at the whole issue from an entirely different angle.

Also, this argument is only as strong as assumptions about personal identity.

Right. I’m assuming that there are human persons, that human persons are enduring entities and that human persons strictly survive through extended periods of time. If you’re willing to deny any one of these claims, then I’ll say “Good day to you sir; this argument will not move you.” But I would ask that you at least make a go at really asking yourself whether you can, upon due reflection, manage to actually bring yourself to believe the denial of one of these claims.

But possibly the metaphysics of mind and personal identity have little to do with each other

I think it is a big fault of many discussions in philosophy of mind that they do not consider questions about the nature of personal identity or questions concerning the metaphysics of material objects, because I think that various stands one takes concerning these issues can greatly constrain what views one may also take concerning the philosophy of mind.

since personal identity is unimportant or indeterminate, in the Parfitian sense.

Yeah, I definitely don’t agree with that. I’m a realist about human persons. In terms of my philosophical methodology, I follow the advice that a professor of mine once gave to his class “Never give up the more obvious for the less obvious.” From my vantage point, giving up realism about human persons in order to take on some obscure thesis in phil mind would be to go against that advice.

Already it's tendentious whether any proper subset of an objects parts is itself an object.

Right. Or, as I would put it, it is tendentious whether any proper subset of the set of a material object’s parts is such that its members also have a mereological sum. That is, it is tendentious whether what Peter van Inwagen has called “the doctrine of arbitrary undetached parts” is true. In fact, Van Inwagen employs the body-minus argument, not to argue that no object can survive the loss of a part, but to argue that, in the scenario, there is no such thing as Body-minus.

But giving up on the view that Body-minus exists either involves adopting mereological nihilism (the view that there are no objects with proper parts) or embracing a view according to which composition occurs but is restricted (i.e. a view according to which it is not always the case that whenever there are two non-overlapping material objects, there is a third object that they both compose).

But if the nihilism is the case, then obviously human persons are not material objects (unless they happen to be material simples – but that view is too wonky to even consider), because there are no material objects to serve as candidates for being human persons.

And I would argue (via the Sider-Lewis argument from vagueness) that if composition is restricted, one of two things must be the case: (a) Either there are metaphysically arbitrary sharp cutoffs that separate cases in which composition occurs from cases in which it doesn’t or (b) it can sometimes be vague whether some objects compose another.

The former is too implausible (in my opinion) to take seriously (although some do). The latter commits one to believing that vagueness is not merely a linguistic phenomenon, that there is genuine vagueness in the world, indeed, that it can be vague whether there is something else in addition to some things we’ve already considered that is composed of those things (not just whether there is something that falls under some specific one of our concepts or satisfies some specific predicate of ours, but whether there is anything there at all). Well, frankly, I find dualism less incredible than I find that. But here is a place where the materialist may well weigh things differently.

Why should I believe that there can be an object such as body-minus that's (roughly) coincident with my body? It of course follows trivially that there are countless such objects. This is deeply implausible. If I'm conscious, then body-minus is conscious. So it follows that there are innumerable conscious objects that aren't identical with me but are varyingly co-extensive with me.

Actually, I see in this the materials for another argument for dualism. I believe that composition is unrestricted; so I believe in all those countless material objects of which you speak. But I don’t believe that any of them are conscious. Denying their existence amounts to committing oneself to nihilism (a live option for the dualist as such, but not for the materialist who is a realist about human persons) or to the view that composition is restricted (the latter of which I take to be problematic for the reason mentioned above).

And if I accept that, it seems I can help myself to a sort of counterpart relation between "body-parts" such that personal identity holds if enough of my "body-parts" exist. Personal identity, on this picture, becomes indeterminate and partial, since, strictly speaking, I can't survive the loss of any of my parts. But closely related physical objects will still exist, and if personal identity consists in *that* then a materialist picture could be maintained.

Then what you would have is not human persons strictly surviving (at least not as human persons) for extended periods of time, but their surviving by way of having non-identical successors. Again, if you can manage to take that view seriously and believe it, more power to you.

I don't know if I accept this. What is body-minus? Just a collection of parts? Well, if it loses the external pinky, it's going to lose some blood, and since blood cells are proper parts of body-minus, body-minus no longer exists.

Since all we need is logical possibility here, let the “god of the philosophers” (not the God that Christians believe in, but the hypothetical one who helps non-hypothetical philosophers in their hypothetical times of need) step conveniently in and help us out by preventing blood loss and that sort of thing. Actually, we don’t even really need her help. If the finger is annihilated instantly, it will take some finite time (however small) for that occurrence to have any additional effects.

I sure hope that you the reason you're preferring annihilation to detachment is just forestall this objection

Actually, it’s because on some views of the metaphysics of material objects (including mine), Body exists just as long as all its parts exist (so, on such views, merely detaching the finger wouldn’t destroy Body; it would merely cause Body to become more spatially scattered).

For example, if you think annihilation if metaphysically possible you have to think something coming into exist ex nihilo is metaphysically possible.

Well, I do think that (and so do a lot of materialists). But no matter anyway. I could run essentially the same argument without having the finder be annihilated. Instead of speaking, in the argument, of human persons strictly surviving the loss of some their parts, I’d speaking of human persons strictly surviving as human persons when some of their parts become detached. It would take some adjustments, but it would be essentially the same line of reasoning. It’s just easier to do it this way.

First of all, it can't be ignored that this is a radically counter-intuitive metaphysics. It entails that no physical objects survive the loss of even a single atom, which means that no physical object has persistance conditions across change.

I don’t think it’s counterintuitive because I don’t think we typically think of the survival of material objects in terms of “strict survival” (as I defined it). I think (similarly to how Chisholm did) of the survival of ordinary material objects in terms of their having appropriately related successors. I don’t think most of us have any strong pre-theoretical beliefs one way or another about this matter; I think we are simply pre-philosophically indifferent when it comes to this subject. I think most of us do have strong pre-theoretical beliefs (or at least strong pre-theoretical intuitions) to the effect that this is not how it goes with us, but (pre-philosophically) who cares whether or not this is how things go with things like couches and cars? Who has an opinion on the matter?

If there's even a plausible way of avoiding this conclusion, I think we should we should take it and run with it, because this is all but compositional nihilism.

It’s not compositional nihilism because, according to this view, there are composite material objects. Furthermore, I believe that there are material objects of the ordinary sort (things like tables and chairs), that there is a sense in which they survive the loss of their parts (in my view, it is that of having appropriate successors), that my van is the same van that I drove away from the dealership (though I don’t think the sort of “sameness” involved here is that of numerical identity), etc. I don’t think I believe anything at all (when it comes to this subject) that is at odds with commonsense (I think I have beliefs concerning it that go beyond the commitments of commonsense, but none which are contrary to it). Although, some philosophers would disagree with me about that (but when are philosophers ever known to agree).

What this argument takes the materialist position to be is that a human person is identical to a certain set of atoms arranged a certain way

No, not that. I agree that no sensible materialist is committed to the view that what a human person is is a set. Presumably, if there are sets, they’re not material objects!

I do take materialists about human persons who are realists about human persons to be committed to the view that human persons aremereological sums of material objects (i.e. that they are things that have material objects as parts and only material objects as parts). And, right away, that commits them to certain substantive views about the metaphysics of material objects (e.g. it commits them, right away, to the falsehood of mereological nihilism). I’m suggesting that if we press further, we can find even more commitments along those lines, and that some of those commitments may not be very attractive.

This coupled with all of the powerful arguments we have against substance dualism makes this argument seem rather weak to me.

I don’t think there are any powerful arguments against substance dualism of the sort that philosophers of mind typically give. But, I know that’s another tendentious claim on my part!

Even if there were nothing I could say in response to this argument as presented, I would still find it far more plausible to take refuge in doubts about the determinacy of personal identity than I would to accept this conclusion.

Fair enough. I actually think that’s a reasonable position to be in. At that point, it’s just a matter of differing initial plausibility assignments.

[JimL]

As I am using it, the term ‘substance dualism’ refers to the thesis that any given human person is (at least in part) composed or constituted by an immaterial substance (aka a soul) or is identical to one (my own view is that human persons are identical to immaterial substances, but that’s a stronger thesis that substance dualism proper).

Substance dualism is not the thesis that bodies have a “dual nature” (whatever that would mean in this context).

To put it in something closer to lay terms, substance dualism is the thesis that human persons have immaterial souls (that they “have them” either by being identical to them or by being partly composed or constituted by them).

ETA: In this thought experiment, there never is a “severed pinky”. Rather, the pinky gets annihilated (that’s important for certain technical reasons).

Well, in laymans terms I think that you are saying that what you believe is that human persons are immaterial substances which are simple and indivisible and which are distinct entities from the material bodies which merely serve to house them. In other words you believe in two substances, aka spirit and matter, two substances which together compose the individual person, the one, the body, divisible and the other, the spirit, or the actual person, indivisible. But if the human person, aka the soul or spirit, is simple and indivisible, how is the substance of which it is composed divisible into many spirits or souls?

[Kenny]

Well, in laymans terms I think that you are saying that what you believe is that human persons are immaterial substances which are simple and indivisible and which are distinct entities from the material bodies

Yes, that is what I believe. At least I believe that souls are simple. People have often inferred from that that they are indivisible. Maybe that’s a good inference, but maybe not. Like I said, I don’t claim to know a lot about the nature of human souls. I just claim to know that there are human souls.

But if the human person, aka the soul or spirit, is simple and indivisible, how is the substance of which it is composed divisible into many spirits or souls?

I don’t hold that human souls are divisible into many souls. I’m not sure what prompted this question.

[ENeGMA]

I’m pretty sure that whatever we are, we’re not those. Maybe our mental states are those, but I’m talking about us, not about our mental states. As I said in the OP, this argument doesn’t have much to do with issues in phil mind. It comes at the whole issue from an entirely different angle.

Well we wouldn't just be abstract Turing machines. We'd be numerically identical to token implementations of that abstract Turing machine of which we are (probably) the only instantiation.

Although now that I think about the issue a little bit, I realize I have no idea what, if anything, people have said about the relationship between personal identity and computational functionalism. It's a little perplexing even to know what to think, as my mental states change all the time, so I can't be identical to a static Turing machine. But I think it's enough for the thesis that at any point in time I'm type identical to a certain computational state of which my brain is a token realizer. And you're going to be right that computational functionalism gives wonky answers in terms of personal identity, at least on some ways of interpreting the view. I could, in the future, become realized in a computer, for instance. But as any committed functionalist would say, "that's not a bug, it's a feature!".

Right. I’m assuming that there are human persons, that human persons are enduring entities and that human persons strictly survive through extended periods of time. If you’re willing to deny any one of these claims, then I’ll say “Good day to you sir; this argument will not move you.” But I would ask that you at least make a go at really asking yourself whether you can, upon due reflection, manage to actually bring yourself to believe the denial of one of these claims.

I think the arguments for this view are rather compelling. Certainly the view sounds crazy, but it's very difficult to resist when you spend a lot of time thinking about different cases of replacement and replication and other such science fiction stuff. At some people you realize you just have no way of answering questions of identity. Maybe you can reason in the other direction and say that, sense substance dualism gives determinate answers, it's to be strongly preferred. But I take this to indicate that our notion of personal identity just is vague or confused, or there are limitations on the accuracy of our conceivability. I think we have strong intuitions about personal identity but I think these are mostly confused, in that any single view you give will have implausible consequences (it seems).

I think it is a big fault of many discussions in philosophy of mind that they do not consider questions about the nature of personal identity or questions concerning the metaphysics of material objects, because I think that various stands one takes concerning these issues can greatly constrain what views one may also take concerning the philosophy of mind.

Prima facie, that's one benefit of the mind-brain identity theory. Of course the mind-brain identity theory is also the theory of mind that is most obviously contradicted by this kind of argument. But if the argument can be defeated in other ways, it's no worse off.

Yeah, I definitely don’t agree with that. I’m a realist about human persons. In terms of my philosophical methodology, I follow the advice that a professor of mine once gave to his class “Never give up the more obvious for the less obvious.” From my vantage point, giving up realism about human persons in order to take on some obscure thesis in phil mind would be to go against that advice.

We wouldn't have to give up realness about human persons, just regard persons the way you regard other material objects. That would be a revision, yes, but I don't see any immediate problems.

Also, it has to be noted that your view gives up the obvious (that objects can survive a change in their parts) for the less obvious. Sure, it's a consequence of THAT move that THIS question seems more complicated. But if we don't make THAT move then we don't have to saying anything implausible in THIS case. If we want to be philosophers of common sense, just deny any of the metaphysical moves that force us to be skeptical of medium-sized objects. That, to me, is always going to giving up the more obvious for the less obvious.

Right. Or, as I would put it, it is tendentious whether any proper subset of the set of a material object’s parts is such that its members also have a mereological sum. That is, it is tendentious whether what Peter van Inwagen has called “the doctrine of arbitrary undetached parts” is true. In fact, Van Inwagen employs the body-minus argument, not to argue that no object can survive the loss of a part, but to argue that, in the scenario, there is no such thing as Body-minus.

But giving up on the view that Body-minus exists either involves adopting mereological nihilism (the view that there are no objects with proper parts) or embracing a view according to which composition occurs but is restricted (i.e. a view according to which it is not always the case that whenever there are two non-overlapping material objects, there is a third object that they both compose).

But if the nihilism is the case, then obviously human persons are not material objects (unless they happen to be material simples – but that view is too wonky to even consider), because there are no material objects to serve as candidates for being human persons.

It's possible that there could be a metaphysical dodge here for the materialist: don't say humans are objects, but say that human persons are processes (whatever THOSE are), or states (whatever THOSE are), or events (whatever THOSE are), or series-of-events (whatever THOSE are).

Trivially, a materialist about persons (on the view you've sketched) is committed to a dead body being a person. But no materialist about persons is committed to dead bodies being people. So charity requires we formulate a more plausible account of the view. So we can say personhood is identical to a bodily process, or a functional role, or whatever.

And I would argue (via the Sider-Lewis argument from vagueness) that if composition is restricted, one of two things must be the case: (a) Either there are metaphysically arbitrary sharp cutoffs that separate cases in which composition occurs from cases in which it doesn’t or (b) it can sometimes be vague whether some objects compose another.

The former is too implausible (in my opinion) to take seriously (although some do).

Timothy Williamson isn't going to be happy about this!

The latter commits one to believing that vagueness is not merely a linguistic phenomenon, that there is genuine vagueness in the world, indeed, that it can be vague whether there is something else in addition to some things we’ve already considered that is composed of those things (not just whether there is something that falls under some specific one of our concepts or satisfies some specific predicate of ours, but whether there is anything there at all). Well, frankly, I find dualism less incredible than I find that. But here is a place where the materialist may well weigh things differently.

Well, this has to be put into the context of the view you accept, which has the consequence that no material object can survive the loss of any of parts, except that since its parts are simples, it always survives the loss of it parts, meaning a tree exists even after its been burnt up in a fire, it's just a very disparate tree, any any mereological sum is an object.

In my best commonsense reflections, I can't see anything to tell between either of those theories as far as common sense goes. Now of course we could have good (or bad) philosophical reasons. But our unguarded judgments about the nature of things just isn't going to help very much here.

Actually, I see in this the materials for another argument for dualism. I believe that composition is unrestricted; so I believe in all those countless material objects of which you speak. But I don’t believe that any of them are conscious. Denying their existence amounts to committing oneself to nihilism (a live option for the dualist as such, but not for the materialist who is a realist about human persons) or to the view that composition is restricted (the latter of which I take to be problematic for the reason mentioned above).

See the next one.

Then what you would have is not human persons strictly surviving (at least not as human persons) for extended periods of time, but their surviving by way of having non-identical successors. Again, if you can manage to take that view seriously and believe it, more power to you.

But you think is fine for ordinary objects. And of course I think I can survive by having non-identical successors. I've survived from childhood to adulthood but I'm not identical my earlier self (we have different properties).

Actually, it’s because on some views of the metaphysics of material objects (including mine), Body exists just as long as all its parts exist (so, on such views, merely detaching the finger wouldn’t destroy Body; it would merely cause Body to become more spatially scattered).

So the tree still exists after it's been burned in fire and it's ashes thrown into the sea.

It's just common sense! What ordinary person could deny this!

I don’t think it’s counterintuitive because I don’t think we typically think of the survival of material objects in terms of “strict survival” (as I defined it). I think (similarly to how Chisholm did) of the survival of ordinary material objects in terms of their having appropriately related successors.

Isn't a common materialist view of personal identity (namely the Psychological view) that survival of persons is having appropriately related successors?

I don’t think most of us have any strong pre-theoretical beliefs one way or another about this matter; I think we are simply pre-philosophically indifferent when it comes to this subject. I think most of us do have strong pre-theoretical beliefs (or at least strong pre-theoretical intuitions) to the effect that this is not how it goes with us, but (pre-philosophically) who cares whether or not this is how things go with things like couches and cars? Who has an opinion on the matter?

Well, since ordinary people don't have an opinion on epistemicism, why not just go with that? Or any other view?

It’s not compositional nihilism because, according to this view, there are composite material objects.

I didn't say it was compositional nihilism, I said it was like compositional nihilism because objects are so brittle. No "ordinary" objects exist in the way we take them to exist.

Furthermore, I believe that there are material objects of the ordinary sort (things like tables and chairs), that there is a sense in which they survive the loss of their parts (in my view, it is that of having appropriate successors), that my van is the same van that I drove away from the dealership (though I don’t think the sort of “sameness” involved here is that of numerical identity), etc. I don’t think I believe anything at all (when it comes to this subject) that is at odds with commonsense (I think I have beliefs concerning it that go beyond the commitments of commonsense, but none which are contrary to it). Although, some philosophers would disagree with me about that (but when are philosophers ever known to agree).

I don't think you're going to get very far convincing someone that the tree in their backyard now isn't identical to the tree it was 5 minutes ago, or even 5 years ago.

Fair enough. I actually think that’s a reasonable position to be in. At that point, it’s just a matter of differing initial plausibility assignments.

I just have a hard time seeing how this argument is going to move a committed materialist. The position being argued against here just doesn't seem in the ballpark of views which, or other materialists, hold dear. Maybe you're right that this is picking up on some hidden commitment we have but don't realize. But more probably, I think, this is showing that mind, personal identity, and these questions in analytic ontology are separable.