Existence, causation and individuation

Suppose a cause C produces horses, in the following way:

• When C produces a horse, a horse instantly comes into existence made out of some mass of non-equine matter M.

• The genetic makeup of the resulting horse is randomly distributed over all DNA compatible with being a horse.

(Imagine lightning striking a bog and randomly turning the bog mass into a horse.)

So now suppose that in world w₁, a female Arabian, Green Lightning, comes into existence as a result of C, while in w₂, a male Exmoor pony, Tigger, comes into existence as a result of C.

Presumably, Green Lightning and Tigger are numerically distinct horses. Why are they distinct? Presumably because they are qualitatively different—specifically, because their DNA is different. If in w₁ and w₂, C respectively produced horses that were exactly alike out of M, those horses would have to have been numerically identical. (Haecceitists will disagree.)

But now we have a puzzle for Aristotelians. Both Green Lightning and Tigger are of the same species. (If you think that breeds or sexes make for different metaphysical species, modify the example and make them be of the same sex and breed, but still very different from each other.) Let the Fs be the qualitative features that Green Lightning and Tigger initially differ in.

1. The Fs in are accidents in the Aristotelian sense: they are accidental to their horsehood, which is their form.

(They may not be accidents in the contemporary modal sense. It may be that it is impossible for a horse to be of another sex than it is.)

But:

2. The Fs make Green Lightning be distinct from Tigger.

3. If what makes Green Lightning be distinct from Tigger are the Fs, then the Fs help make Green Lightning be Green Lightning.

4. Nothing that helps make x be x can be explanatorily posterior to x.

5. So, the Fs are not explanatorily posterior to Green Lightning. (2-4)

6. The accidents of x are explanatorily posterior to x.

7. So, the Fs are explanatorily posterior to Green Lightning. (1,6)

8. Contradiction! (5,7)

The case where C makes a horse come into existence from non-equine matter makes the above argument a bit more vivid. In the ordinary case of equine reproduction, a sperm and egg contribute their DNA and give rise to the DNA of the offspring. There it could be argued that the relevant thing that helps make the resulting horse be the horse it is is the DNA in the sperm and the DNA in the egg.

One could conclude that a horse can’t come into existence from matter that doesn’t already contain implicit in it the DNA of the horse. But that is implausible, especially since God could create a horse even without any matter.

This puzzle worries me a lot. I initially thought it was a special puzzle for four-dimensionalist temporal-parts Aristotelianism, because it showed that the first temporal part of the horse was explanatorily prior to the whole, whereas Aristotelianism forbids parts to be prior to wholes. But then I realizes that the same point could be made about accidents without reference to four-dimensionalism.

Here is my best solution. There is something about Green Lightning that is prior to her being Green Lightning. It is her being caused by C to exist with the Fs (i.e., her being caused by C to exist as a female Arabian, etc.). Admittedly, that sounds just as much as an accident of Green Lightning as the Fs are. It’s not Green Lightning’s form, so what else could it be but an accident? There is no answer in Aristotle, but there is a potential answer in Aquinas: this could be Green Lightning’s act of being, her esse. And it is not crazy to take Green Lightning’s esse to be something that (a) is prior to Green Lightning, (b) Green Lightning could not exist without, and (c) an individuator of Green Lightning.

This reminds me of a line of thought in the Principle of Sufficient Reason book where I argued that the esse of a contingent being is its being caused. If my present solution is correct, that was only a partial description of the esse of a contingent being. And I think there may well be an argument for the principle that ex nihilo nihil fit in the vicinity, just as in the PSR book—for it is absurd to think that anything contingent could be prior to x if x has no cause, while this esse is something contingent.

Progress report on books

My Necessary Existence book with Josh Rasmussen is right now in copyediting by Oxford.

I am making final revisions to the manuscript of Infinity, Causation and Paradox, with a deadline in mid October. As of right now, I've finished revising five out of ten chapters.

I am toying with one day writing a book on the ethics of love.

A problem for some Humeans

Suppose that a lot of otherwise ordinary coins come into existence ex nihilo for no cause at all. Then whether a given coin lies heads or tails up is independent of how all the other coins lie in the sense that no information about the other coins will give you any data about how this one lies.

It is crucial here that the coins came into existence causelessly. If the coins came off an assembly line, and a large sample were all heads-up, we would have good reason to think that the causal process favored that arrangement and hence that the next coin to be examined will also be heads-up.

But now suppose that I know that Humeanism about laws is true, and there is a very, very large number of coins lying in a pile, all of which I know for sure to have come to be there causelessly ex nihilo, and there are no other coins in the universe. Suppose, further, that in fact all the coins happen to lie heads-up. Then when the number of coins is sufficiently large (say, of the order of magnitude of the number of particles in the universe), on Humean grounds it will be a law of nature that coins begin their existence in the heads-up orientation. But if the independence thesis I started the post with is true, then no matter how many coins I examined, I would not have any more reason to think that the next unexamined coin is heads than that it is tails. Thus, in particular, I would not be justified in believing in the heads-up law.

One might worry that I couldn’t know, much less know for sure, that the coins are there causelessly ex nihilo. A reasonable inference from the fact that lots of examined coins are all heads-up would seem to be that they were thus arranged by something or someone. And if I made that inference, then I could reasonably conclude that the coins are all heads-up. But my conclusion, while true and justified, would not be knowledge. I would be in a Gettier situation. My justification depends essentially on the false claim that the coins were arranged by something or someone. So even if one drops the assumption that I know that the coins are there causelessly ex nihilo, I still don’t know that the heads-up law holds. Moreover, my reason for not knowing this has nothing to do with dubious theses about the infallibility of knowledge. I don’t know that the heads-up law holds, whether fallibly or infallibly.

There is no problem for the Humean as yet. After all, there is nothing absurd about there being hypothetical situations where there is a law but we can’t know that it obtains. But for any Humean who additionally thinks that our universe came into existence causelessly, there is a real challenge to explain why the laws of our world are not like the heads-up law—laws that we cannot know from a mere sample of data.

This problem is fatal, I think, to the Humean who thinks that our universe started its existence with a large number of particles. For the properties of the particles would be like the heads-up and tails-up orientations of the coins, and we would not be in a position to know all particles fall into some small number of types (as the standard model in particle physics does). But a Humean scientist who doesn’t think the universe has a cause could also think that our universe started its existence with a fairly simple state, say a single super-particle, and this simple state caused all the multitude of particles we observe. In that case, the order-in-multiplicity that we observe would not be causeless, and the above argument would not apply.

Sentencing to time served

Sometimes people are sentenced to “time served”: the time they spent in jail prior to trial is retroactively counted as their sentence. But doesn’t justice call for harsh treatment to be imposed as a punishment? The jail time, however, was not imposed on the malefactor as a punishment—it was imposed on a person presumed innocent to negate a probability of flight. How can it turn into a punishment retroactively?

Well, one solution is to reject a retributive account of punishment. Another is to say that justice is served by such punishment.

But I think there is a less revisionary approach. Instead of saying that justice calls for harsh treatment to be imposed, say that justice calls for one to ensure something harsh happening as a result of the crime. Sometimes, one ensures a state of affairs by causally imposing it. But one can also ensure a state of affairs by verifying the occurrence of the state of affairs while being committed to causing the state of affairs if that were to fail.

This provides a way for a retributivist to accept the intuition that if someone is paralyzed for life as a result of trying to blow a bank vault, there need be no further call to send them to prison—one may be able to ensure more than sufficient punishment simply by verifying that the paralysis occurred as a result of the crime. Another way for the retributivist to accept that intuition would be to say that while we didn’t impose the paralysis on the robber as a punishment, God did. But the move from imposing to ensuring allows the retributivist to avoid mixing up God in human justice here.

Uncountable independent trials

Suppose that I am throwing a perfectly sharp dart uniformly randomly at a continuous target. The chance that I will hit the center is zero.

What if I throw an infinite number of independent darts at the target? Do I improve my chances of hitting the center at least once?

Things depend on what size of infinity of darts I throw. Suppose I throw a countable infinity of darts. Then I don’t improve my chances: classical probability says that the union of countably many zero-probability events has zero probability.

What if I throw an uncountable infinity of darts? The answer is that the usual way of modeling independent events does not assign any meaningful probabilities to whether I hit the center at least once. Indeed, the event that I hit the center at least once is “saturated nonmeasurable”, i.e., it is nonmeasurable and every measurable subset of it has probability zero and every measurable superset of it has probability one.

Proposition: Assume the Axiom of Choice. Let P be any probability measure on a set Ω and let N be any non-empty event with P(N)=0. Let I be any uncountable index set. Let H be the subset of the product space Ω^I consisting of those sequences ω that hit N, i.e., ones such that for some i we have ω(i)∈N. Then H is saturated nonmeasurable with respect to the I-fold product measure P^I (and hence with respect to its completion).

One conclusion to draw is that the event H of hitting the center at least once in our uncountable number of throws in fact has a weird “nonmeasurable chance” of happening, one perhaps that can be expressed as the interval [0, 1]. But I think there is a different philosophical conclusion to be drawn: the usual “product measure” model of independent trials does not capture the phenomenon it is meant to capture in the case of an uncountable number of trials. The model needs to be enriched with further information that will then give us a genuine chance for H. Saturated nonmeasurability is a way of capturing the fact that the product measure can be extended to a measure that assigns any numerical probability between 0 and 1 (inclusive) one wishes. And one requires further data about the system in order to assign that numerical probability.

Let me illustrate this as follows. Consider the original single-case dart throwing system. Normally one describes the outcome of the system’s trials by the position z of the tip of the dart, so that the sample space Ω equals the set of possible positions. But we can also take a richer sample space Ω^* which includes all the possible tip positions plus one more outcome, α, the event of the whole system ceasing to exist, in violation of the conservation of mass-energy. Of course, to be physically correct, we assign chance zero to outcome α.

Now, let O be the center of the target. Here are two intuitions:

1. If the number of trials has a cardinality much greater than that of the continuum, it is very likely that O will result on some trial.

2. No matter how many trials—even a large infinity—have been performed, α will not occur.

But the original single-case system based on the sample space Ω^* does not distinguish O and α probabilistically in any way. Let ψ be a bijection of Ω^* to itself that swaps O and α but keeps everything else fixed. Then P(ψ[A]) = P(A) for any measurable subset A of Ω^* (this follows from the fact that the probability of O is equal to the probability of α, both being zero), and so with respect to the standard probability measure on Ω^*, there is no probabilistic difference between O and α.

If I am right about (1) and (2), then what happens in a sufficiently large number of trials is not captured by the classical chances in the single-case situation. That classical probabilities do not capture all the information about chances is something we should already have known from cases involving conditional probabilities. For instance P({O}|{O, α}) = 1 and P({α}|{O, α}) = 0, even though O and α are on par.

One standard solution to conditional probability case is infinitesimals. Perhaps P({α}) is an infinitesimal ι but P({O}) is exactly zero. In that case, we may indeed be able to make sense of (1) and (2). But infinitesimals are not a good model on other grounds. (See Section 3 here.)

Thinking about the difficulties with infinitesimals, I get this intuition: we want to get probabilistic information about the single-case event that has a higher resolution than is given by classical real-valued probabilities but lower resolution than is given by infinitesimals. Here is a possibility. Those subsets of the outcome space that have probability zero also get attached to them a monotone-increasing function from cardinalities to the set [0, 1]. If N is such a subset, and it gets attached to it the function f_N, then f_N(κ) tells us the probability that κ independent trials will yield at least one outcome in N.

We can then argue that f_N(κ) is always 0 or 1 for infinite. Here is why. Suppose f_N(κ)>0. Then, κ must be infinite, since if κ is finite then f_N(κ)=1 − (1 − P(N))^κ = 0 as P(N)=0. But f_N(κ + κ)=(f_N(κ))², since probabilities of independent events multiply, and κ + κ = κ (assuming the Axiom of Choice), so that f_N(κ)=(f_N(κ))², which implies that f_N(κ) is zero or one. We can come up with other constraints on f_N. For instance, if C is the union of A and B, then f_C(κ) is the greater of f_A(κ) and f_B(κ).

Such an approach could help get a solution to a different problem, the problem of characterizing deterministic causation. To a first approximation, the solution would go as follows. Start with the inadequate story that deterministic causation is chancy causation with chance 1. (This is inadequate, because in the original dart-throwing case, the chance of missing the center is 1, but throwing the dart does not deterministically cause one to hit a point other than the center.) Then say that deterministic causation is chancy causation such that the failure event F is such that f_F(κ)=0 for every cardinal κ.

But maybe instead of all this, one could just deny that there are meaningful chances to be assigned to events like the event of uncountably many trials missing or hitting the center of the target.

Sketch of proof of Proposition: The product space Ω^I is the space of all functions ω from I to Ω, with the product measure P^I generated by the product measures of cylinder sets. The cylinder sets are product sets of the form A = ∏_i∈IA_i such that there is a finite J ⊆ I such that A_i = Ω for i ∉ J, and the product measure of A is defined to be ∏_i∈JP(A_i).

First I will show that there is an extension Q of P^I such that Q(H)=0 (an extension of a measure is a measure on a larger σ-algebra that agrees with the original measure on the smaller σ-algebra). Any P^I-measurable subset of H will then have Q measure zero, and hence will have P^I-measure zero since Q extends P^I.

Let Q₁ be the restriction of P to Ω − N (this is still normalized to 1 as N is a null set). Let Q₁^I be the product measure on (Ω − N)^I. Let Q be a measure on Ω defined by Q(A)=Q₁^I(A ∩ Ω^N). Consider a cylinder set A = ∏_i∈IA_i where there is a finite J ⊆ I such that A_i = Ω whenever i ∉ J. Then
Q(A)=∏_i∈JQ₁(A_i − N)=∏_i∈JP(A_i − N)=∏_i∈JP(A_i)=P^N(A).
Since P^N and Q agree on cylinder sets, by the definition of the product measure, Q is an extension of P^N.

To show that H is saturated nonmeasurable, we now only need to show that any P^I-measurable set in the complement of H must have probability zero. Let A be any P^I-measurable set in the complement of H. Then A is of the form {ω ∈ Ω^I : F(ω)}, where F(ω) is a condition involving only coordinates of ω numbered by a fixed countable set of indices from I (i.e., there is a countable subset J of I and a subset B of Ω^J such that F(ω) if and only if ω|_J is a member of B, where ω|_J is the restriction of ω to J). But no such condition can exclude the possibility that a coordinate of Ω outside that countable set is in H, unless the condition is entirely unsatisfiable, and hence no such set A lies in the complement of H, unless the set is empty. And that’s all we need to show.

Naturalists about mind should be Aristotelians

1. If non-Aristotelian naturalism about mind is true, a causal theory of reference is true.

2. If non-Aristotelian naturalism about mind is true, then normative states of affairs do not cause any natural events.

3. If naturalism about mind is true, our thoughts are natural events.

4. If a causal theory of reference is true and normative states of affairs do not cause any thoughts, then we do not have any thoughts about normative states of affairs.

5. So, if non-Aristotelian naturalism about mind is true, then we do not have any thoughts about normative states of affairs. (1-4)

6. I think that I should avoid false belief.

7. That I should avoid false belief is a normative state of affairs.

8. So, I have a thought about a normative state of affairs. (6-7)

9. So, non-Aristotelian naturalism about mind is not true. (5 and 8)

Note that the Aristotelian naturalist will deny (2), for she thinks that normative states of affairs cause natural events through final (and, less obviously, formal) causation, which is a species of causation.

I think the non-Aristotelian naturalist’s best bet is probably to deny (2) as well, on the grounds that normative properties are identical with natural properties. But there are now two possibilities. Either normative properties are identical with natural properties that are also “natural” in the sense of David Lewis—i.e., fundamental or “structural”—or not. A view on which normative properties are identical with fundamental or “structural” natural properties is not a plausible one. This is not plausible outside of Aristotelian naturalism. But if the normative properties are identical with non-fundamental natural properties, then too much debate in ethics and epistemology threatens to become merely verbal in the Ted Sider sense: “Am I using ‘justified’ or ‘right’ for this non-structural natural property or that one?”

Location, causation and transsubstantiation

Here’s a fun thought experiment. By a miracle (say) I am sitting in my armchair in Waco but my causal interaction with my environment at the boundaries of my body would be as if I were in Paris. There is a region of space in Paris shaped like my body. When a photon hits the boundary of that region, it causally interacts with me as if I were in Paris: I have the causal power to act at a distance to reflect Parisian photons as if I were in that region in Paris. Alternately, that photon might be absorbed by me: I have the causal power to absorb Parisian photons. As a result, it looks to Parisians like I am in Paris, and as I look around, it looks to me like Paris is all around me. The same is true for other interactions. When my vocal cords vibrate, instead of causing pressure changes in Texan air, they cause pressure changes in chilly France. As I walk, the region of space shaped like my body in Paris that is the locus of my interaction with Parisians moves in the usual way that bodies move.

Furthermore, my body does not interact with the environment in Waco at all. Wacoan photons aimed at my body go right through it and so I am invisible. In fact, not just photons do that: you could walk right through my body in Waco without noticing. My body is unaffected by Texan gravity. It is simply suspended over my sofa. As I wave my hand, my hand does in fact wave in Texas, but does not cause any movement of the air in Texas—but in Paris, the region of space in which I interact with the Parisians changes through the wave, and the air moves as a result. When I eat, it is by means of Parisian food particles that come to be incorporated into my Wacoan body.

To me, to Wacoans and to Parisians it looks in all respects like I am in Paris. But I am in Waco.

Or am I? There is a view on which the causal facts that I’ve described imply that I am in Paris, namely the view that spatial relationships reduce to causal relationships. It is an attractive view to those like me who like reductions.

But this attractive view threatens to be heretical. Christ’s body is here on earth in the Eucharist, as well as in heaven in the more normal way for a body to be. But while the body is surely visible in heaven and interacts with Mary and any other embodied persons in heaven, it does not interact physically with anything on earth. Granted, there is spiritual interaction: Christ’s presence in the Eucharist is a means of grace to recipients. But that probably isn’t the sort of interaction that would ground spatial location.

There is, however, a way to modify the causal reduction of location that handles the case of the Eucharist. Actual causal interactions do not seem to be enough to ground location. The reduction very likely needs needs dispositional causal interactions that typically ground causal counterfactuals like:

1. If Parisians were to shine a flashlight into that dark alley, they’d see me.

However, dispositions can be masked. For instance, sugar is still soluble even if God has promised to miraculously keep it from dissolving when it is placed in water. In such a case, the sugar still has the disposition to dissolve in water, but fails to ground the counterfactual:

2. The lump would be dissolved were it placed in water.

We might, thus, suppose that when the Mass is being celebrated in Waco, Christ comes to have the dispositional causal properties that would ordinarily be contitutive of his being present in Waco, such as the disposition to reflect Texan photons, and so on. But by miracle, all these dispositions are masked and do not result in actual causal interaction. The unmasked dispositions are those corresponding to spiritual interaction.

Here’s an interesting lesson. The kind of causal-reductive view of location that I’ve just considered seems to be one of the least transsubstantiation-congenial views of location. But, nonetheless, the transsubstantiation can still be made sense of on that view when the view is refined. This gives us evidence that transsubstantiation makes sense.

And we can now go back to the story of my being in Waco while interacting in Paris. The story was underspecified. I didn’t say whether I have the dispositions that go with being in Waco. If I do, these dispositions are being miraculously masked. But they may be enough to make me count as being in Waco. So on the story as I’ve told it, I might actually be both in Waco and in Paris.

Final question: Can external temporal location be similarly causally grounded? (Cf. this interesting paper.)

Teleology and the direction of time

It would be depressing to think that one will never swim as fast as one is swimming today. But it would uplifting to think that that one has never swum as fast as one is swimming today.

I used to think the direction of time was defined by the predominant direction of causation. That may be the case, but if one takes humanistic cases like the above as central, one might think that perhaps the predominant direction of teleology is a better way to define the direction of time. Of course, telê are there to be achieved, and so the direction of teleology needs to fit well with the direction of causation, at least in the case of things that concern us. Moreover, there is some reason to think that teleology is behind all causation—causation aims at an effect.

Rapid cell replacement: A failed argument against materialism

I thought I had a nice argument against materialism, but it didn’t work out. Still, it’s fun to think about the argument and why it doesn’t work.

Start with this plausible thesis, which seems at least naturally necessary:

1. If any cell in a human body blinks out of existence and a new cell, exactly like the one before, blinks into existence sufficiently quickly in the same orientation, then the result would not interrupt the human’s life or any train of consciousness.

Now imagine that very, very quickly one-by-one every cell in my body blinks out of existence and is replaced by a new cell formed by a coincidental quantum fluctuation. Moreover, suppose each replacement happens sufficiently quickly in the sense of (1), and indeed so quickly that all of the replacements are done in less than the blink of an eye. Applying claim (1) billions of times, I conclude that neither my existence nor my train of consciousness would be interrupted by this process.

But if materialism is true, the resulting entity would have insufficient causal connection to me to be me. Thus, if materialism is true, I would have to cease to exist as a result of these rapid replacements. But it seems this would violate (1) at some point. (Moreover, the resulting being would not be the product of natural selection, so on evolutionary functionalist theories, the being would not have mental states. Furthermore, in any case, its brain states would not have the kinds of connections with the external world that give rise to content according to the best materialist theories, so its thoughts would be largely contentless.)

But the argument I just gave doesn’t work. First, (1) is false in the case of a human zygote, since the destruction of one’s only cell would kill one. What made (1) plausible was the thought that we had many cells, and the replacement of any one of them with a randomly produced cell would make no difference. So, (1) needs to be modified to remain plausible:

2. If any cell in a human body consisting of many cells blinks out of existence and a new cell, exactly like the one before, blinks into existence sufficiently quickly in the same orientation, then the result would not interrupt the human’s life or any train of consciousness.

But now it no longer follows that a quick cell-by-cell replacement would have to keep me alive. For here is a possible hypothesis: For a replacement cell to come to be a part of the body, it has to come to be sufficiently causally intertwined with the rest of the body. This takes some time. It could well be that if the cells are replaced one by one in less than the blink of an eye, the new cells don’t have time to become intertwined with the rest of the body. Thus, the body comes to have fewer and fewer cells as the gradual replacement process continues. If the replacement process were to stop, pretty quickly the replacement cells would come to be causally intertwined with the veteran cells, and would come to be a part of the body. But it doesn’t stop. As a result, eventually the process leads to a state where I don’t have “many” cells in my body, and hence (2) becomes inapplicable.

What if, on the other hand, the replacement is done more slowly, so that there is time for cells to causally intertwine and become a part of the body? Then there need be no problem for materialism, because now the resulting entity does have a sufficient causal connection to me to be me.

There is, of course, a vagueness problem for the materialist: When do I cease to exist in the process? But that's another argument. I think typical materialists who think that they exist cannot escape vague existence.

Instantaneous Newtonian gravitational causation at a distance?

It’s widely thought that Newtonian gravity, when causally interpreted, involves instantaneous causation at a distance. But I think this is technically not right.

Suppose we have two masses m₁ and m₂ with distance r apart at time t₁. The location of m₂ at t₁ causes m₁ to accelerate at t₁ towards m₂ of magnitude Gm₂/r². And this sure looks like instantaneous causation at a distance.

But this isn’t an instance of instantaneous causation. For facts about what m₁’s acceleration is at t₁ are not facts about how the mass is instantaneously at t₁, but facts about how the mass is at t₁ and at times shortly before and after t₁: acceleration is the rate of change of velocity over time. Suppose that a poison ingested at t₁ caused Smith to be dead at all subsequent times. That wouldn’t be a case of instantaneous causation, even though we could say: “The poison caused t₁ to be the last moment of Smith’s life.” For the statement that t₁ is the last moment of Smith’s life isn’t a statement about what the world is instantaneously like at t₁, but is a conjunctive statement that at t₁ he’s alive (that part isn’t caused by the poison) and that at times after t₁ he’s dead (that part is caused by the poison, but not instantaneously). Similarly, m₁’s velocity (and position) at times after t₁ is caused by m₂’s location at t₁, but m₁’s velocity (or position) at t₁ itself is inot.

Let’s call cases where a cause at t₁ causes an effect at interval of times starting at, but not including, t₁ a case of almost instantaneous causation. In the gravitational case, what I have described so far is only almost instantaneous causation. Of course, people balking at instantaneous action at a distance are apt to balk at almost instantaneous action at a distance, but the two are different.

The above is pretty much the whole story about instantaneous Newtonian causation if one is not a realist about forces. But if one is a realist about forces, then things will be a bit more complicated. For m₂’s location at t₁ causes a force on m₁ at t₁, which complicates the causal story. On the bare story above, we had m₂’s location causing an acceleration of m₁. When we add realism about forces, we have an intermediate step: m₂’s location causes a force on m₁, which force then causes an acceleration of m₁. (There might even be further complications depending on the details of the realism about forces: we may have component forces causing a net force.) Now, when the force-at-t₁ causes an acceleration-at-t₁, this is, for the reasons given above, a case of almost instantaneous causation. But the causing of the force-at-t₁ by the location-at-t₁ of m₂ is a case of genuinely instantaneous causation.

But is it a case of causation at a distance? It seems to be: after all, the best candidate for where the force on m₁ is located is that it is located where m₁ is, namely at distance r from m₂. (There are two less plausible candidates: the force acting on m₁ is located at m₂, and almost instantaneously pulls on m₁; or it’s bilocated between the two locations; in any case, those candidates won’t improve the case for instantaneous action at a distance.) But here is another problem. The force on m₁ is not produced by m₂. It is produced by m₁ and m₂ together. After all, the Newtonian force law is Gm₁m₂/r². (It is only when we divide the force by m₁ to get the acceleration that m₁ disappears.) Rather than m₂ pulling on m₁, we have m₁ and m₂ pulling each other together. Thus, m₂ instantaneously partially causes the force on m₁ at a distance. But the full causation, where m₁ and m₂ cause the force on m₁, is not causation at a distance, because m₂ is at the location of that force.

In summary, the common thought that Newtonian gravitation involves instantaneous causation at a distance is wrong:

• If forces are admitted as genuine causal intermediates (“realism about forces”), then we have almost instantaneous causation of acceleration by force (moreover, not at a distance), and instantaneous partial causation of force at a distance.

• Absent force realism, we have almost instantaneous causation at a distance.

Humean metaphysics implies Cartesian epistemology

Let’s assume two theses:

1. Humean view of causation.

2. Mental causalism: mental activity requires some mental states to stand in causal relations.

If I accept these two theses, then I can a priori and with certainty infer a modest uniformity of nature thesis. Here’s why. On mental causalism, mental activity requires causation. On Humeanism, causation depends on the actual arrangement of matter. If the regularities found in my immediate vicinity do not extend to the universe as a whole, then they are no causal laws or causal relations. Thus, given causalism and Humeanism, I can infer a priori and with certainty from the obvious fact that I have mental states that there are regularities in the stuff that my mind is made of that extend universally. In other words, we get a Cartesian-type epistemological conclusion: I think, so there must be regularity.

In other words, Humean metaphysics of nature plus a causalist theory of mind implies a radically non-Humean epistemology of nature. The most plausible naturalist theories of mind all accept causalism. So, it seems, that a Humean metaphysics of nature plus naturalism—which is typically a part of contemporary Humean metaphysics—implies a radically non-Humean epistemology of nature.

So Humean metaphysics and epistemology don’t go together. So what? Why not just accept the metaphysics and reject the epistemology? The reason this is not acceptable is that the Cartesian thesis that the regularity of nature follows with certainty from what I know about myself is only plausible (if even then!) given Descartes’ theism.

Infinity, Causation and Paradox

I've just signed a contract with Oxford for this book, with a manuscript delivery date in September.

Presentists can't reduce time

Historically, some philosophers have attempted to reduce time to something else, say change or the causal nexus. It's interesting to note that this cannot be done if presentism is true. For to reduce time to something else requires giving a nontemporal account of the "wholly earlier" relation between events. But if presentism is true, there never exist two events one of which is wholly earlier than the other. For if one of them is present, the other is not. And only present events exist given presentism.

Now, of course, the presentist has a way of talking about non-present events. She can, for instance, use the temporal modal operators WAS and WILL. However, she cannot do so in the course of reducing time to something else, since WAS and WILL already presuppose time. The presentist must take time to be primitive, thus.

In particular, this means that Aristotle, who attempted to reduce time to change, cannot be consistent if he is a presentist.

A simple causal theory of the arrow of time

Typical causal theories of time say that the order of time is determined by the order of causal relationships between events in time. This tends to be a difficult theory to develop, if only because of the possibilities of simultaneous causation and time travel. But suppose with substantivalists that there really are moments (or intervals) of time. Then it is possible to have a very simple and elegant theory of the order of time:

1. Time u is prior to time v if and only if time u causes time v.

This theory is, I suppose, inspired by Tooley's idea that earlier points of spacetime cause later ones. It has no worries about the possibility of simultaneous causation. For even if there is simultaneous causation, there is no simultaneous causation between times, since distinct times can never be simultaneous (if u and v are times and they are simultaneous, they are the same time--and of course nothing can cause itself). Likewise, while there is some cost in denying time travel and backwards causation, one can accept time travel and backwards causation while denying that a later time can cause an earlier one.

There is also an interesting and slightly more complex variant:

2. Time u is prior to time v if and only if some event at u at least partially causes v.

This variant, too, is compatible with simultaneous and backwards causation between events--it just rules out simultaneous or backwards causation between an event and a time. It has the advantage that perhaps the dynamic evolution of times isn't just causally driven by earlier times, but by the events at those earlier times. For instance, if a time is a maximal spacelike hypersurface, it is very natural to think on the grounds of General Relativity that the distribution of matter at earlier times causes that hypersurface. We can, further, deem each time's existence to be an event that happens at that time. If we do that, then (2) becomes a generalization of (1).

From causal finitism to divine simplicity

If God is not simple, he has infinitely many really distinct features. Moreover infinitely many of these features will be involved in creation, e.g., because there are infinitely many reasons that favor the creation of this world, and for each reason God will plausibly have a distinct feature of being impressed by that reason. But causal finitism (the doctrine that infinitely many things can't come together causally) rules this out. So divine simplicity is true.

Assuming causal finitism, the thing that one might challenge is the claim that infinitely many of God's features are causally efficacious.

There is an even easier argument for divine simplicity based if actual infinites are impossible. For, surely, either (a) God is simple or (b) God has infinitely many really distinct features. If actual infinites are impossible, that rules out (b).

What I am up to

My main philosophical project for the summer is cleaning up the draft of Infinity, Causation and Paradox. I've done the content cleanup in chapters 1-4 (bibliography is another thing) so far.

Naturalism and second-order experiences

My colleague Todd Buras has inspired this argument:

1. A veridical experience of an event is caused by the event.
2. Sometimes a human being is veridically experiencing that she has some experience E at all the times at which E is occurring.
3. If (1) and (2), then there is intra-mental simultaneous event causation.
4. If naturalism about the human mind is true, there is no intra-mental simultaneous causation.
5. So, naturalism about the human mind is not true.

In this argument, (4) is a posteriori: if naturalism is true, mental activity occurs at best at the speed of light. I am sceptical about (2) myself.

That nasty oxygen

We think of gasoline, lighter fluid and hydrogen as dangerous flammable substances (in the ordinary, not philosophical, sense). But in the ordinary course of things, when they burn, they do so because of oxygen. So it seems more reasonable to think of oxygen as the dangerous inflamer here. This is of course a very standard example in philosophy of causation: we don't normally think of oxygen as the cause of a fire, but we could just as well, except for pragmatic stuff. I just didn't realize until recently how great the example is. Having oxygen about is having a fire about to happen. Thinking about this also makes it clear just how precarious our existence is, dependent on such a highly dangerous chemical as it is.

Experiencing present events and simultaneous causation

When I look at a rock, I see the rock and not just its outside surface. Of course, it is the outside layer that is causally responsible for my perception: a typical rock would look the same (except when intense light was shining through it) if suddenly all but the outer one millimeter of it disappeared. Similarly, when I see an event like a ball flying through the air, I see an event that includes the ball's presently flying through the air, even though it is only the temporal parts of the event fractions of a second prior to my perception that are causally responsible for my perception, since it takes light a few of nanoseconds to get to me from the ball and then it takes my visual apparatus rather longer to process it, and I need to process data from two different times in order to get the perception of motion. In both cases the data is processed without my being aware of it, and a rock or an event that includes the present is presented to me. If all goes well, this is veridical, though it could happen that there is no rock but a mere shell or that the ball was annihilated just before I had the perception.

So, in these experiences, when things go well, I have an experience of something extended through space and/or time caused by a very small proper part of the object of the experience. But veridical experiences must be caused by their objects (and in the right way). This means that a whole can count as causing something that is only caused by a proper part. (There are, of course, plenty of non-perceptual examples.) Moreover, notice that the case of the ball flying through the air, then, is a case of something like simultaneous causation when all goes well: a temporally extended event of the ball flying--including its flying now--causes my present perception, and the two events temporally overlap.

But this instance of simultaneous causation seems grounded in a case of non-simultaneous causation: a past temporal part of the ball's flight causing a present experience. That may be so. However, for all we know this non-simultaneous causation could be grounded in a finite sequence of fundamental simultaneous causations between temporally-extended temporally-simple events.

Minimizing the number of fundamental relations between concreta

An interesting metaphysics project that could use more work is to minimize the number of fundamental non-intentional relations between substances. How few can we do with? I think it would be really great if one could reduce the number of such relations to a handful of relations, or at least determinable families of relations. There is only one candidate really clear to me: causation. I think it would be an interesting research project to adopt the working hypothesis that causation is the one and only such relation and see how things go.

A lot of people will want to add parthood to this list, but I don't think a substance can be a part of another substance. (Parts are grounded in wholes, and substances are not grounded in other things.) Spatial relations like being seven meters apart (on relationalism about locations) and being located at (on substantivalism about locations) are a family of plausible candidates.