Memory theories of personal identity and faster-than-light dependence

Consider this sequence of events:

• Tuesday: Alice’s memory is scanned and saved to a hard drive.
• Wednesday: Alice’s head is completely crushed in a car crash.
• Thursday: Alice’s scanned memories are put into a fresh brain.

It seems that on a memory theory of personal identity, we would say that fresh brain on Thursday is Alice.

But now suppose that on Thursday, Alice’s scanned memories are put into two fresh brains.

If one of the operations is in the absolute past—the backwards light-cone—of the other, it is easy to say that what happens is that Alice goes to the brain that gets the memories first.

Fine. But what if which brain got the memories first depends on the reference frame, i.e., the two operations are space-like separated? It’s plausible that this is a case of symmetric fission, and in symmetric fission Alice doesn’t survive.

But now here is an odd thing. Suppose the two operations are simultaneous in some frame, but one happens on earth and the other on a spaceship by alpha-Centauri. Then whether Alice comes into existence in a lab on earth depends on what happens in a spaceship that’s four light-years away, and it depends on it in a faster-than-light way. That seems problematic.

Killing coiled and straight snakes

Suppose a woman crushes the head of a very long serpent. If the snake all dies instantly when its head is crushed, then in some reference frame the tail of the snake dies before the woman crushes the head, which seems wrong. So it seems we should not say the snake dies instantly.

I am not talking about the fact that the tail can still wiggle a significant amount of time after the head is crushed, or so I assume. That’s not life. What makes a snake be alive is having a snake substantial form. Death is the departure of the form. If the tail of the headless snake wiggles, that’s just a chunk of matter wiggling without a snake form.

What’s going on? Presumably it’s that metaphysical death—the separation of form from body—propagates from the crushed head to the rest of the snake, and it propagates at most at the speed of light. After all, the separation is a genuine causal process, and we are supposed to think that genuine causal processes happen at the speed of light or less.

So we get a constraint: a part of the snake cannot be dead before light emitted from the head-crushing event could reach the part. But it is also plausible that as soon as the light can reach the part, the part is dead. For a headless snake is dead, and as soon as the light from the head-crushing event can reach a part, the head-crushing event is in the absolute past of the part, and so the part is a part of a headless snake in every reference frame. Thus the part is dead.

So death propagates to the snake exactly at the speed of light from the head-crushing, it seems. Moreover, it does this not along the snake but in the shortest distance—that’s what the argument of the previous paragraph suggests. That means that a snake that’s tightly coiled into a ball dies faster than one that is stretched out when the head is crushed. Moreover, if you have a snake that is rolled into the shape of the letter C, and the head is crushed, the tail dies before the middle of the snake dies. That’s counterintuitive, but we shouldn’t expect reality to always be intuitive.

Darwin and Einstein against the shared-form interpretation of Aristotle

Assume an Aristotelian account of substantial form on which forms are found in the informed things. A classic question is whether substantial forms are shared between members of the same kind or whether each individual has their own numerically (but maybe not qualitatively) distinct form.

Here’s a fun argument against the shared-form view. For evolution to work with substantial forms, sometimes organisms of one metaphysical kind must produce organisms of another kind. For instance, supposing that wolves are a different metaphysical kind from dogs, and dogs evolved from wolves, it must have happened that two wolves reproduced and made a dog. (I suspect wolves and dogs are metaphysically the same kind, but let’s suppose they aren’t for the sake of the argument.) If we are to avoid occasionalism about this, we have to suppose that the two wolves had a causal power to produce a dog-form under those circumstances.

Plausibly dogs evolved from wolves in Siberia, but there was also a Pleistocene wolf population in Japan, and imagine that the causal power to produce a dog was found in both wolf populations. Suppose, counterfactually, that a short period of time after a pair of wolves produced a dog in Siberia, a pair of Japanese wolves also produced a dog. On a shared-form view, when the Siberian wolves produced a dog, they did two things: they produced a dog-form and they made a dog composed of the dog-form and matter. But when the Japanese wolves produced a dog, the dog-form already existed, so they only thing they could do is make a dog composed of matter and that dog-form.

The first oddity here is this. Our (perhaps imaginary) Japanese wolves didn’t know that there was already a dog in Siberia, so when they produced a dog, they exercised exactly the same causal powers that their Siberian cousins did. But their exercise of these causal powers had a different effect, because it did not produce a new form, since the form already existed, and instead it made the form get exemplified in some matter in Japan. It is odd that the exercise of the same causal power worked differently in the same local circumstances.

Second, there is an odd action-at-a-distance here. The dog-form was available in Siberia, and somehow the Japanese wolves in the story made matter get affected by it thousands of kilometers away.

In fact, to make things worse, we can suppose the Japanese wolves only lagged a two or three milliseconds after their Siberian cousins. In that case, the Siberian wolves caused the existence of the dog-form, which then affected the coming-into-existence of a dog in Japan in a faster-than-light way. Indeed, in some reference frames, the Japanese dog came into existence shortly before the dog-form came into existence in Siberia. In those reference frames we have backwards causation: the Siberian wolves make a dog-form and that dog form organizes matter in Japan earlier.

If, on the other hand, every dog has a numerically distinct form, there is no difficulty: the Japanese wolves’ activity can be entirely causally independent of the Siberian ones’.

Of snakes and cerebra

Suppose that you very quickly crush the head of a very long stretched-out serpent. Specifically, suppose your crushing takes less time than it takes for light to travel to the snake’s tail.

Let t be a time just after the crushing of the head.

Now causal influences propagate at most at the speed of light or less, the crushing of the head is the cause of death, and at t there wasn’t yet time for the effects of the crushing to have propagated to the tip of the tail. Furthermore, assume an Aristotelian account of life where a living thing is everywhere joined with its form or soul and death is the separation of the form from the matter. Then at t, because the effects of crushing haven’t propagated to the tail, the tail is joined with the snake’s form, even though the head is crushed and hence presumably no longer a part of the snake. (Imagine the head being annihilated for greater clarity.)

Now as long as any matter is joined to the form, the critter is alive. It follows that at time t, the snake is alive despite lacking a head. The argument generalizes. If we crush everything but the snake’s tail, including crushing all the major organs of the snake, the snake is alive despite lacking all the major organs, and having but a tail (or part of a tail).

So what? Well, one of the most compelling arguments against animalism—the view that people are animals—is that:

1. People can survive as just a cerebrum (in a vat).

2. No animal can survive as just a cerebrum.

3. So, people are not animals.

But presumably the reason for thinking that an animal can’t survive as just a cerebrum is that a cerebrum makes an insufficient contribution to the animal functions. But the tail of a snake makes an even less significant contribution to the animal functions. Hence:

4. If a snake can survive as just a tail, a mammal can survive as just a cerebrum.

5. A snake can survive as just a tail.

6. So, a mammal can survive as just a cerebrum.

Objection: Only physical effects are limited to the speed of light in their propagation, and the separation of form from matter is not a physical effect, so that instantly when the head is crushed, the form leaves the snake, all at once at t.

Response: Let z be the spacetime location of the tip of the snake’s tail at t. According to the object, at z the form is no longer present. Now, given my assumption that crushing takes less time than it takes for light to travel to the snake’s tail, and that in one reference frame w is just after the crushing, there will also be a reference frame according to which z is before the crushing has even started. If at z the form is no longer present, then the form has left the tip of the tail before the crushing.

In other words, if we try to get out of the initial argument by supposing that loss of form proceeds faster than light, then we have to admit that in some reference frames, loss of form goes backwards in time. And that seems rather implausible.

Absolute reference frame

Some philosophers think that notwithstanding Special Relativity, there is a True Absolute Reference Frame. Suppose this is so. This reference frame, surely, is not our reference frame. We are on a spinning planet rotating around a sun orbiting the center of our galaxy. It seems pretty likely that if there is an absolute reference frame, then we are moving with respect to it at least at the speed of the flow of the Local Group of galaxies due to the mass of the Laniakea Supercluster of galaxies, i.e., at around 600 km/s.

Given this, our measurements of distance and time are actually going to be a little bit objectively off the true values, which are the ones that we would measure if we were in the absolute reference frame. The things we actually measure here in our solar system will be objectively off due to time dilation and space contraction by about two parts per million, if my calculations are right. That means that our best possible clocks will be objectively about a minute(!) off per year, and our best meter sticks will be about two microns off. Not that we would notice these things, since the absolute reference frame is not observable, so we can’t compare our measurements to it.

As a result, we have a choice between two counterintuitive claims. Either we say that duration and distance are relative, or we have to say that our best machining and time measuring is necessarily off, and we don’t know by how much, since we don’t know what the True Absolute Reference Frame is.

Physicalism, consciousness and history

Many physicalists think that conscious states are partly constituted by historical features of the organism. For instance, they think that Davidson’s swampman (who is a molecule-by-molecule duplicate of Davidson randomly formed by lightning hitting a swamp) does not have conscious states, because swampman lacks the right history (on some views, one just needs a history of earlier life, and on others, one needs the millenia of evolutionary history).

I want to argue that probably all physicalists should agree that conscious states are partly constituted by historical features.

For if there is no historical component to the constitution of a conscious state, and physicalism is true, then conscious states are constituted by the simultaneous arrangement of spatially disparate parts of the brain. But consciousness is not relative to a reference frame, while simultaneity is.

Here’s another way to see the point. Suppose that conscious states are not even partly constituted by the past. Then, surely, they are also not even partly constituted by the past. In other words, conscious states are fully constituted by how things are on an infinitesimally thin time-slice. On that view, it would be possible for a human-like being, Alice, to exist only for an instant and to be conscious at that instant. But now imagine that in inertial reference frame F, Alice is a three-dimensional object that exists only at an instant. Then it turns out that in every other frame than F, Alice’s intersection with a simultaneity hyperplane is two-dimensional—but she also has a non-empty intersection with more than one simultaneity hyperplane. Consequently, in every frame other than F, Alice exists for more than an instant, but is two-dimensional at every time. A two-dimensional slice of a human brain can’t support consciousness, so in no frame other than F can Alice be conscious. But then consciousness is frame-relative, which is absurd.

Once we have established:

1. If physicalism is true, conscious states are partly constituted by historical features,

it is tempting to add:

2. Conscious states are not even partly constituted by historical features.

3. So, physicalism is not true.

But I am not very confident of (2).

If materialism is true, we can't die in constant pain

Here is an unfortunate fact:

1. The last minute of your life can consist of constant conscious pain.

Of course, I think all pain is conscious, but I might as well spell it out. The modality of the “can” in this post will be something fairly ordinary, like some sort of nomic possibility.

Now say that a reference frame is “ordinary for you” provided that it is a reference frame corresponding to something moving no more than 100 miles per hour relative to your center of mass.

Next, note that switching between reference frames should not turn pain into non-pain: consciousness is not reference-frame relative. Thus:

2. If the last minute of your life consists of constant conscious pain, then in every reference frame that is ordinary for you, in the last half-minute of your life you are in constant conscious pain.

Relativistic time-dilation effects of differences between “ordinary” frames will very slightly affect how long your final pre-death segment of pain is, but will not shorten that segment by even one second, and certainly not by 30 seconds.

Next add:

3. If materialism is true, then you cannot have a conscious state when you are the size of a handful of atoms.

Such a small piece of the human body is not enough for consciousness.

But now (1)–(3) yield an argument against materialism. I have shown here that, given the simplifying assumption of special relativity, in almost every reference frame, and in particular in some ordinary frames, your life will end with you being the size of a handful of atoms. If materialism is true, in those frames towards the very end of your life you will have to exist without consciousness by (3), and in particular you won’t be able to have constant conscious pain (or any other conscious state) for your last half-minute.

Aquinas's embryology and the theory of relativity

Aquinas famously thinks that there is a succession of forms in utero, with first a vegetable form, then an animal form, and then a rational animal (human) form. No two of these forms are had simultaneously.

But if a three-dimensionally extended object that has form A comes to be a three-dimensionally extended object that has form B, with no other forms intervening, then, in every inertial reference frame except for at most one, there is a time at which some of the matter has form A and some of the matter has form B. So unless there is a privileged frame, Aquinas’s story doesn’t work.

In the following diagram, the slanted dashed line indicates a reference frame where some of the matter has form A (red) and some has B (blue).

Here is a variant that could work, but does not seem very plausible. We could imagine that when we have a transition from A to B, the matter of A, except at one point, passes to B through one or more other forms, indicated by the yellow portion of the diagram. These might be forms of mere particles, or they could be some special forms. In other words, A dies off into a point, with the dead matter acquiring transitional forms, and then B starts growing from the last point of A, incorporating the transitional forms. Where the A and B substances meet will be a point either of A or of B, but not of both. The narrowing of A and the growth of B happen at the speed or light or less.

On this variant, no inertial frame contains both A and B points. (If light moves at 45 degrees from horizontal in the diagram, then inertial frames correspond to lines like the dashed one making a less than 45 degree angle with the horizontal.)

But there is something rather weird going on here. Suppose that A is the vegetable form and B is the animal form (a similar argument will apply if A is the animal form and B the human form). Then close to the pointy meeting between A and B, the yellow stuff contains the vast majority of what biology would call “the embryo”, and a fairly well-developed one, since it’s on the cusp of becoming an animal. Yet the vast majority of that “embryo” is the yellow stuff—neither the vegetable nor the animal, but something else, maybe mere atoms. Indeed, once we get close enough to the meeting point, the yellow will materially function just like an embryo, since a tiny subatomic hole makes no difference to material functioning. This is very odd, and gives us reason to reject Aquinas’s story.

Of course, the main alternative to Aquinas’s story is that the gametes change into a human being. That faces some of the same difficulties. However, I think the difficulties are less if the gametes are not themselves a substance, but a plurality of substances, perhaps particle-substances. In the diagram below, the gamete-stuff is in yellow, and the blue indicates the human being. We still have the problem that early on most of what we have will need to be biologically very close to a functioning zygote, and yet it is in yellow, except for a small blue hole corresponding to where ensoulment is spreading out from a single point. But I think this is less problematic, because at this juncture the yellow stuff is something that is less obviously an organism. (Admittedly, the blue stuff is less obviously an organism when it is nearly a point. But what makes it an organism is that while its matter has little going for it, it’s got the right form.)

So, relativity makes it hard to hold on to Aquinas’s embryology. Which is a nice thing for pro-life Thomists who want to defend ensoulment at conception and hence deny Aquinas's embryology--or Catholic Thomists who find the doctrine of the Immaculate Conception incompatible with that embryology.

Maybe there is some way of getting out of this by using the considerations from yesterday’s post, though.

Even more on pointy beginnings

In a recent post I argued that in Aristotelian substantial change, given special relativity, the resultant substance starts as basically a point—it is arbitrarily small.

I think the argument doesn’t actually require much in the way of Aristotelian assumptions, but works for any caused extended substance, or at least any ordinary one.

Suppose that a substance B is caused to exist by A (which might be a single entity or a plurality) and initially (at least) at distinct points in spacetime. There is a reference frame according to which one of these points is earlier than the other (this is true in all frames if the points are timelike-related and some frames if they are spacelike-related). Let F be a frame where this happens, and let z₁ be the F-earlier and z₂ the F-later point. From now on, work in F.

Let t_i be the time of z_i. Now B is at least partly present arbitrarily close to z₁, and hence arbitrarily close to t₁, and since t₁ < t₂, it follows that B already existed before t₂. Therefore, any causal influence of A sufficiently close to time t₂ is irrelevant to B’s existence. In fact, B wasn’t even partly caused by A to exist at times close to t₂, since it had already existed for a while before this. And this contradicts our assumption that A caused B at both z₁ and z₂.

A crucial assumption here is that nothing that happens later than a time t is relevant to whether a substance B exists at t.

What if there is backwards causation? If so, then this argument fails. But even if there is backwards causation, it is rare and extraordinary. It is still true that in ordinary cases, substances are caused to exist at a single point.

What if B is uncaused? Again, the argument fails. But even if there are uncaused extended substances, they are not the norm. So, again, the argument still works in ordinary cases.

I will be very small

I have a counterintuitive view that our bodies can be extremely defective, to the point that we can exist with a body that’s just a couple of atoms. But counterintuitive as this view is, I have an argument for it.

Start with this little geometric result about Minkowski spacetime. Think of a reference frame F as a maximal set of spacelike hyperplanes called F-times. If T is an F-time, and K is a region of spacetime, then the T-slice of K is the intersection of K and T.

Proposition. Let K be a bounded non-empty region of spacetime. The following is true for almost every reference frame F. For every ϵ > 0, there are F-times T₁ and T₂ less than ϵ apart, with the properties that (a) all of K is temporally before T₂ (according to F), (b) the T₁-slice of K is non-empty, and for any F-time T between T₁ and T₂ inclusive, and any two points w and z in the T-slice of K, the F-distance between w and z is less than ϵ.

(This follows from the result here. We can identify a reference frame with wthe future-facing unit normal vector of its times, and then “almost every” is understood with respect to the Lebesgue measure on the unit sphere.)

For simplicity, and as the approximation is surely appropriate, assume that special relativity is right. Let K be the four-dimensional region occupied by my body during my life. Assume K is bounded, which sure seems intuitively plausible (there are some quantum issues here which I will ignore for now). Then it follows from the Proposition that, according to almost every reference frame, there is a time T₂ within a nanosecond of my death such that the T₂-slice of my body (or the region K occupied by it) is less than a nanoneter in size.

So not only can I be really small, but I will be really small, according to most reference frames.

Relativity and an argument for incompatibilism

A common argument for the incompatibility of freedom and determinism goes something like this (where premises 1, 2 and 3 are implicitly assumed to hold at all times):

1. It is currently possible that I will do A only if the past and the laws are compatible with my future doing of A.

2. If determinism is true, then the past and the laws are only compatible with my future doing of what I will in fact do.

3. So, if determinism is true, the only things that it is currently possible that I will do are the things that I will in fact do.

4. Freedom requires that at some time it be possible that I will do something other than what I will in fact do.

But given relativity theory, it is not clear what “the past” means in the above arguments, since past is always relative to some reference frame. There are at least four ways of reading (1):

• Strongest: It is now possible for me to do A only if the events in the complement of my present closed future light-cone and the laws are compatible with my doing A.

• Stronger: It is now possible for me to do A only if for every reference frame R, the past according to R and the laws are compatible with my doing A.

• Weaker: It is now possible for me to do A only if for some reference frame R, the past according to R and the laws are compatible with my doing A.

• Weakest: It is now possible for me to do A only if the events in my present open past light-cone and the laws are compatible with my doing A.

Now, generally we should prefer less strong premises. So we should avoid the Strongest and Stronger readings of (1). But I claim that the analogue of (2) is unjustified if we take the Weaker reading of (1). For suppose A would be a future action. Then the past open light-cone of A will be strictly larger than my current past open light-cone. Determinism tells us that A or its absence is nomically determined by the events in its past open light-cone. But that past open light-cone is strictly larger than my current past open light-cone. And it could be that some event E that is in A’s past open light-cone but not in my current past open light-cone makes a difference as to whether A happens. Then there will be a reference frame R such that this event E would be outside my current past according to R. Thus, A’s or its absence’s being determined by the events in its past open light-cone leaves open the possibility that some event E that isn’t in my current past according to R makes a difference as to whether A happens, and hence that A or its absence need not be determined by the events in my current past according to R.

So, for the argument (1)–(4) to work given relativity, it seems we need the Stronger or Strongest reading for (1).

Is there a better way to fix the argument relativistically? Maybe. I like the idea of replacing (1) with an atemporal formulation:

5. Action A is only free if its non-occurrence is compatible with the laws and the subset of events in A’s causal history that are outside of my life.

Teleportation and time-travel

Let’s assume:

1. Faster-than-light travel is metaphysically possible in a special relativistic world.

And let’s assume:

2. In a special relativistic world, no (inertial) reference frames are metaphysically privileged.

Now, if faster-than-light travel occurs, then one travels from space point z₁ to point z₂ during a length of time t < d(z₁, z₂)/c according to some reference frame F₁. The arrival location then is not in the light-cone centered on the departure point (and light-cones do not depend on reference frames). But if the arrival point is not in the light-cone centered on the departure point, then there is a reference frame F₂ according to which the arrival is earlier than the departure. (For the forward light-cone centered on a point a is just the set of points of space-time that are later than or simultaneous with a according to all frames. So if you’re not in the forward light-cone centered on a, you are earlier than a according to at least one frame.)

But no frame is privileged by (2). Moreover, if faster than light travel is possible, then faster than light travel is possible at any finite speed, since anything else would be unacceptably ad hoc. So if faster than light travel is possible according to F₁, it is possible according to F₂. So let’s suppose that you traveled from z₁ to z₂ and arrived −δ units of time earlier according to F₂ (for some δ > 0). Then add another spot of faster than light travel from z₂ to z₁, at a speed high enough to ensure you arrive at z₁ in δ/2 units of time. Then according to F₂, you moved from z₁ to z₂ and back to z₁ and arrive −δ + δ/2 = −δ/2 units of time after the beginning of your journey.

So according to F₂ you time-traveled backwards at the same spatial location. But backwards time-travel at the same spatial location in one reference frame implies backwards time-travel according to all frames (because it implies going into one’s backwards light cone).

So, we’ve argued:

3. If (1) and (2) are true, then it is metaphysically possible to travel absolutely backwards in time,

where absolute backwards time-travel is time-travel backwards according to all inertial frames. (I assume that most people working in philosophy of time know this.)

And there is good reason to believe (1) and (2). Indeed, (2) seems definitional. And (1) seems pretty plausible, especially given an omnipotent God. After all, surely God could make you travel to alpha Centauri and back by Christmas of this year. Note, though, that a part of (1)—and perhaps this is the controversial part?—is the possibility of a special relativistic world.

I am not sure what to make of this.

Individuating substances by their matter

According to traditional Aristotelianism, what makes you and me be distinct entities is that although we are of the same species, we’re made of distinct chunks of matter.

Here is a quick initial problem with this. The matter in us changes. It is quite possible that someone has different matter at age 1 and at age 20, and so by the Aristotelian individuation criterion, they are a different entity of the same species at ages 1 and 20, which is false.

One way out of this is to embrace presentism. But presentism is incompatible with the Aristotelian conviction that truth supervenes on being.

Another move is to narrow down the individuation criterion to say that:

1. Conspecifics x and y are made distinct by their being simultaneously made of different chunks of matter.

There are two problems with this move.

First, time travel. If at age 20, with different matter, you enter a time machine and travel back to meet yourself back when you were 1, then 20-year-old you and 1-year-old you are made of different chunks of matter at the same time. And while many problems about time travel are solved by moving from external to internal time, that doesn’t work here. For one cannot say that matter individuates x and y at the same internal time, since internal time is a concept that only makes sense when you are dealing with a single substance.

Second, relativity theory and teleportation (which is also kind of like time travel). Suppose that by age 20 you have different matter from what you had at age 1. Then God teleports 20-year-old you 100 light-years away instantly or nearly instantly (with respect to some reference frame). Then there will be a reference frame with respect to which it is true that the teleported 20-year-old you is simultaneous with 1-year-old you. So either simultaneity with respect to that reference frame doesn’t count—and that leads us to a privileged reference frame, contrary at least to the spirit of relativity—or else you are not yourself, which is absurd.

While one can swallow the idea that time travel is impossible, spacelike teleportation seems clearly possible.

Here is another move: we replace (1) with:

2. Conspecifics x and y are made distinct by their originating in distinct chunks of matter.

And 20-year-old you, no matter how they travel in space and/or time, has originated in the same chunk of matter as 1-year-old you.

This move has a cost: it requires that we be somewhat non-realist about substantial change. Full-blown realism about substantial change requires the matter to stay in existence while the substance changes. But if matter can stay in existence when its substance perishes, then that matter could be re-formed into another substance of the same species, which would violate the origination-restricted indviduation criterion. On (2), we have to accept the theory that the matter of a thing perishes when the substance does. This removes one of the major motivations behind positing matter: namely, that matter is supposed to explain why a corpse looks like the living body (viz., because it is allegedly made of the same matter).

Note, too, that (2) has a serious ambiguity once we have insisted that matter does not survive substantial change. By the chunk of matter that a substance originates in, do we mean the last chunk of matter before the substance’s existence or the first chunk of matter in the substance?

If we mean the last chunk of matter before the substance’s existence, there are two problems. First, it seems ad hoc to single out one aspect of the causes of the substance—the earlier matter—as doing the individuating. It seems better to individuate by means of the causes, applying the converse of the essentiality of origins. Second, it seems possible for an object to come into existence without prior matter. (If God exists, this is clear, since God creates ex nihilo. If God doesn’t exist, then very likely the world came into existence ex nihilo.) But then it seems quite possible for two objects of the same species to come into existence without prior matter. (Though if one wants to dispute this, one might point to the fact that a literal reading of the biblical creation account has God making the first two humans out of chunks of preexisting matter—soil and rib respectively. Maybe there is a deep metaphysical reason why this has to be so, and perhaps the initial ex nihilo created things had to be all of different species. But I just don’t find the latter requirement that plausible.)

So perhaps in (2) we mean the first chunk of matter in the substance. But if matter does not survive substantial change, then it seems plausible that the identity of the substance is prior to the identity of its initial matter, and hence the identity of the substance cannot come from its initial matter. This isn’t a very strong argument. Maybe the initial matter is prior to the substance, and has an identity of its own, while later matter is posterior to the substance.

So, our best version of the Aristotelian individuation account is this:

3. Conspecifics x and y are made distinct by their each having a different first chunk of matter.

Finally, it is interesting to note that (2) and (3) are only plausible if it is impossible for a material substance to have no beginning. But our best account for why a material substance cannot have a beginning is causal finitism. So those who like the Aristotelian account of individuation—I am not one of them—have another reason to accept causal finitism.

Perdurance, physicalism and relativity

Here is a very plausible thesis:

1. Exactly one object is a primary bearer of my present mental states.

This is a problem for the conjunction of standard perdurance, physicalism and special relativity. For according to standard perdurance on physicalism:

2. The primary bearers of my mental states are time slices.

Now consider all the time-slices of me that include my present mental states. There will be many of them, since there will be one corresponding to each reference frame. On relativistic grounds none of them is special. Thus:

3. Either all or none of them are the primary bearers of my present mental states.

If all of them are the primary bearers of my present mental states, we violate 1. If none of them are, then there is no primary bearer of my present mental states by 2, which also violates 1.

Simultaneity, A-Theory and Relativity

Here is a standard story about Special Relativity and the A-theory of time:

• There is an objective metaphysical simultaneity, but

• this metaphysical simultaneity does not affect physical events and is unobservable.

Let’s assume the A-theory is correct and this story is also correct.

Now, when people talk about this metaphysical simultaneity, they normally think they it aligns with the frame-relative simultaneity of Special Relativity for some privileged reference frame. This seems reasonable. But it is an interesting question to ask for an explanation of this alignment.

Causation may put some constraints on metaphysical simultaneity. For instance, perhaps, there shouldn’t be any possibility of future to past causation. But a metaphysical simultaneity relation can satisfy such constraints without coinciding with any frame-relative simultaneity.

If God exists, I guess we might suppose that metaphysical simultaneity coincides with a frame-relative simultaneity because it’s more elegant if it does.

Entanglement

Suppose two quantum systems, A and B, are perfectly entangled in such a way that for any measurement of one system, the other system must have an exactly corresponding (for simplicity) measurement.

Here’s one causal story that can be given about this that is compatible with both special relativity insofar as it presupposes no preferred reference frame and yet respects the commonplace intuition that there is no backwards causation.

The story assumes that quantum systems can communicate with each other faster than light, but not absolutely temporally backwards. Specifically, if system A at point a in spacetime is not in the future light cone of point b, then system A at a can send a signal to a system at point b. This saves much of the intuition that there is no backwards causation.

Here is what happens in entanglement cases. Suppose you are one of the two systems and you are being measured.

1. You uniformly choose a random real number x between 0 and 1, and send out a superluminal message “I am being measured and I picked x” to the other entangled system to arrive at the time of the other system’s measurement—unless the other system’s measurement is in your future, in which case your message doesn’t arrive.

2. You check for receipt of a superluminal “I am being measured and I picked y” message from the other twin.

3. If you don’t get the message, then you are designated the Boss of the Measurement.

4. If you do get the message, then you are designated the Boss of the Measurement if and only if x > y.

5. If you are designated the Boss of the Measurement, then you now collapse your own state according to the Born rule probabilities, and send a superluminal message “I am the Boss and I collapsed to state z”.

6. If you are not designated the Boss of the Measurement, then you are almost sure to receive a message of the form “I am the Boss and I collapsed to state z”, so you collapse to the entangled state corresponding to the other system’s state z.

The sequence of tasks 1-6 either happens super-fast or they are all temporally simultaneous but explanatorily sequential. Furthermore, the messaging is hidden from us: the choice of the real numbers x and y, the messages sent and Boss status are all hidden variables.

Notes:

A. The setup has a possibility, but with zero probability, of failure—namely, if both systems randomly chose the same number (i.e., x = y), then neither is Boss of the Measurement and collapse doesn’t happen.

B. According to some but not all reference frames the superluminal messaging will result in messages arriving before they are sent (i.e., the receipt is spacelike separated from the sending). But if the superluminal messaging is limited to the above kinds of messages, hopefully one can ensure that causal loops are ruled out, and so no paradox ensues. And there is no absolutely-backwards causation.

C. Locality is violated by the superluminal messaging, of course. But having a causal explanation is more important than ensuring locality.

D. With more than two systems entangled, things get much more complicated.

E. If the entanglement isn’t perfect, things get much more complicated.

Perdurance, Relativity and Quantum Mechanics

It is known that perdurantists, who hold that objects persisting in time are made of infinitely thin temporal slices, have to deny that fundamental particles are simple (i.e., do not have (integral) parts). For a fundamental particle is an object persisting in time, and hence will be made of particle-slices.

But what is perhaps not so well-known is that on perdurantism, the temporal slices a particle is made of will typically not be simple either, given some claims from standard interpretations of Quantum Mechanics and Special Relativity. The quick version of the argument is this: the spatial non-localizability of quantum particles requires typical temporal slices to be non-localized simples (e.g., extended simples), but this runs into relativistic problems.

Here is a detailed argument.

A perdurantist who takes Relativity seriously will say that for each inertial reference frame R and each persistent object, the object is made of R-temporal slices, where an R-temporal slice is a slice all of whose points are simultaneous according to R.

Now, suppose that p is a fundamental particle and that p is made up of a family F₁ of temporal slices defined by an inertial reference frame R₁. Now, particles are rarely if ever perfectly localized spatially on standard interpretations of Quantum Mechanics (Bohmianism is an exception): except perhaps right after a collapse, their position is fuzzy and wavelike. Thus, most particle-slices in F₁ will not be localized at a single point. Consider one of the typical unlocalized particle-slices, call it S. Since it’s not localized, S must cover (be at least partially located at) at least two distinct spacetime points a and b. These points are simultaneous according to R₁.

But for two distinct spacetime points that are simultaneous according to one frame, there will be another frame according to which they are not simultaneous. Let R₂, thus, be a frame according to which a and b are not simultaneous. Let F₂ be the family of temporal slices making up p according to R₂. Then S is not a part (proper or improper) of any slice in F₂, since S covers the points a and b of spacetime, but no member of F₂ covers these two points. But:

1. If a simple x is not a part of any member of a family F of objects, then x is not a part of any object made up of the members of that family.

Thus, if S is simple, then S is not a part of our particle p, which is absurd. Therefore, for any reference frame R and particle p, a typical R-temporal slice of p is not simple.

I think the perdurantist’s best bet is supersubstantialism, the view that particles are themselves made out of points of spacetime. But I do not think this is a satisfactory view. After all, two bosons could exist for all eternity in the same place.

Without Relativity, the problem is easily solved: particle-slices could be extended simples.

It is, I think, ironic that perdurantism would have trouble with Relativity. After all, a standard path to perdurantism is: Special Relativity → four-dimensionalism → perdurantism.

I myself accept four-dimensionalism but not perdurantism.

My experience of temporality

This morning I find myself feeling the force of presentism. I am finding it hard to see my four-dimensional worm theory as adequately explaining why my experience only includes what I am experiencing now, instead of the whole richness of my four-dimensional life. I am also finding it difficult to satisfactorily explain the sequentiality of my experiences: that I will have different experiences from those that I have now, some of which I dread and some of which I anticipate eagerly.

When I try to write down the thoughts that make me feel the force of presentism, the force of the thoughts is largely drained. After all, to be fair, when I wrote that I have am having trouble “explaining why my experience only includes what I am experiencing now”, shouldn’t I have written: “explaining why my present experience only includes what I am experiencing now”, a triviality? And that mysterious sequentiality, is that anything beyond the fact that some of my experiences are in the future of my present experience?

The first part of the mystery is due to the chopped up nature of my consciousness on a four-dimensional view. Instead of seeing my life as a whole, as God sees it, I see it in very short (but probably not instantaneous) pieces. It is puzzling how my consciousness can be so chopped up, and yet be all mine. But we have good reason to think that this phenomenon occurs outside of temporality. Split brain patients seem to have such chopped up consciousnesses. And if consciousness is an operation of the mind’s, then on orthodox Christology, the incarnate Christ, while one person, had (and still has) two consciousnesses.

Unfortunately, both the split brains and the Incarnation are mysterious phenomena, so they don’t do much to take away the feeling of mystery about the temporal chopping up of the consciousness of my four-dimensional life. But they do make me feel that there is no good argument for presentism here.

The second part of the mystery is due to the sequentiality of the experiences. As the split brain and Incarnation cases show, the sequentiality of experiences in different spheres of consciousness is not universal. The split brain patient has two non-sequential, simultaneous spheres of consciousness. Christ has his temporal sphere (or spheres, if we take the four-dimensional view) of consciousness and his divine atemporal sphere of consciousness. But seeing the contingency of the sequentiality does not remove the mystery in the sequentiality.

It makes me feel a little better when I recall that the presentist story about the sequentiality has its own problems. If my future experiences aren’t real—on presentism they are nothing but stuff in the scope of a modal “will” operator that doesn’t satisfy the T axiom—then what am I anticipating or dreading? It seems I am just here in the present, and when I think about this, it feels just as mysterious as on four-dimensionalism what makes the future impend. Of course, the presentist can give a reductive or non-reductive account of the asymmetry between past and future, but so can the four-dimensionalist.

So what remains of this morning’s presentist feelings? Mostly this worry: Time is mysterious and our theories of time—whether eternalist or presentist—do not do justice to its mysteriousness. This is like the thought that qualia are mysterious, but when we give particular theories of them—whether materialist or dualist—it feels like something is left out.

But what if I forget about standard four-dimensionalism and presentism, and just try to see what theory of time fits with my experiences? I then find myself pulled towards a view of time I had when I was around ten years old. Reality is four-dimensional, but we travel through it. Future sufferings I dread are there, ahead of me. But I am not just a temporal part among many: there is no future self suffering future pains and enjoying future pleasures. The past and future have physical reality but it’s all zombies. As for me, I am wholly here and now. And you are wholly here and now. We travel together through the four-dimensional reality.

But these future pains and pleasures, how can they be if they are not had by me or anyone else? They are like the persisting smile of the Cheshire cat. (I wasn’t worried about this when I was ten, because I was mainly imagining myself as traveling through events, and not philosophically thinking about my changing mental states. It wasn’t a theory, but a way of thinking.) Put that way, maybe it’s not so crazy. After all, the standard Catholic view of the Eucharist is that the accidents of bread and wine exist without anything having them. So perhaps my future and past pains and pleasures exist without anyone having them—but one day I will have them.

Even this strange theory, though, does not do justice to sequentiality. What makes it be the case that I am traveling towards the future rather than towards the past?

And what about Relativity Theory? Why don’t we get out of sync with one another if we travel fast enough relative to one another? Perhaps the twin who travels at near light speed comes back to earth and meets only zombies, not real selves? That seems absurd. Maybe though the internal flow of time doesn’t work like that.

I do not think this is an attractive theory. It is the theory that best fits most of my experience of temporality, and that is a real consideration in favor of it. But it doesn’t solve the puzzle of sequentiality. I think I will stick with four-dimensionalism. For now. (!)

Acting without existing (any more)

Thesis: It is possible for an object to be acting while it does not exist.

Argument:

Imagine a rattlesnake that is ten light-years long, all stretched out. For all one hundred years of life it has been deliberately rattling its rattle. And then at the end of its hundred years, its head is destroyed, and I assume that the destruction of the head of a snake is sufficient for its death.

Rattling continues for at least about ten years even after the snake is dead, since the nerve signals the brain had sent while the snake was alive are continuing to rattle.

If this post-mortem rattle counts as the snake’s activity, the Thesis is established. But it is not clear that this ten years of post-mortem rattle is the snake’s activity.

But now consider the last year of pre-mortem rattling, call it R₉₉ (since it starts in year 99 of the snake’s life). Whatever one says of the post-mortem rattling, clearly R₉₉ is the snake’s activity. However, there is a reference frame—the way I set the length of the snake and the times in the story guarantees this—in which R₉₉ occurs after the snake’s head has been destroyed, and hence occurs after the death of the snake. But R₉₉ is the snake’s activity. Hence, there is a reference frame where an activity of the snake occurs after the snake is dead.

Scholium:

Obviously, only existent things can act. But while existence simpliciter is important for activity, existence-at-a-time does not have the same kind of significance. Obviously, often an actor’s action has a relationship R to some thing x that the actor itself does not have. For instance, an agent’s action may be known by me without the agent being known by me (here, R is being known and x is me).

Now, when we say that Elizabeth II exists as Queen of Canada, that is just an awkward way of saying that she has a monarchic relationship to Canada, rather than being a claim about that mysterious thing deep ontology studies: existence. I think we should think of existing-at-a-time as not really existence but simply as a particular kind of relationship—an occupation or presence relationship. It is not surprising in general that activities can stand in relationships that the agents do not. So, why can’t an activity stand in an occupation relationship to a time that the agent does not?

I think much confusion in philosophy comes from thinking of existence-at-a-time and existence-in-a-place as something special, somehow deeply ontologically different from other relations.

Informed organs surviving the death of an individual

In my last post, I offered a puzzle, one way out of which was to accept the possibility of informed bits of an animal surviving the death of the animal. But the puzzle involved a contrived case--a snake that was annihilated.

But I can do the same story in a much more ordinary context. Jones is lying on his back in bed, legs stretched out, with healthy feet, and dies of some brain or heart problem. How does the form (=soul) leave his body? Well, there are many stories we can tell. But here's one thing that's clear: the form does not leave the toes before leaving the rest of the body. I.e., either the toes die (=are abandoned by the form) last or they die simultaneously with the rest. But in either case, then Special Relativity and the geometry of the body (the fact that one can draw a plane such that one or more toes are on one side of the plane, and the rest of the body is on the other) imply that there is a reference frame in which the form leaves one or more of the toes last. Thus, there will be a reference frame and a time at which only toes or parts of toes are informed. It is implausible to think that one is alive if all that's left alive are the toes. So organs can survive death while informed by the individual's form.