Fields and finetuning

Here is an interesting fine-tuning issue, inspired by a talk I heard from Brian Cutter at the 2023 ACPA meeting.

It seems likely that physical reality will involve one or more fields: objects that assign values to points in space (“ordinary” space or configuration space), which values then govern the evolution of the universe.

The fine-tuning issue is this. A plausible rearrangement principle should allow any mathematical assignment of values of the field to the points in space as metaphysically possible. But intuitively “most” such assignments result in a configuration that cannot meaningfully evolve according to our laws of nature. So we want to have an explanation of the fine-tuning—why are we so lucky as to have an assignment that plays nice with the laws of nature.

For a toy example, consider an electric field, which is a vector field E that generates a force F = qE on a particle of charge q. Intuitively, “most” vector fields will be nonmeasurable. But for a nonmeasurable electric field, we have no hope for a meaningful solution to the differential equations of motion. (OK, I’m ignoring the evolution of the field itself.)

For another example, suppose we think of the quantum wavefunction as a function over configuration space rather than as a vector in Hilbert space (though I prefer the latter formulation). If that function is nonmeasurable—and intuitively “most” are nonmeasurable—then we have no way to use quantum mechanics to predict the further evolution of this wavefunction. And if that function, while measurable, is not square integrable (I don’t know if there is a sense of “most” that applies here), then we have no way to use the Born rule to generate measurement predictions.

Metaphysical semiholism

For a while I’ve speculated that making ontological sense of quantum mechanics requires introducing a global entity into our ontology to ground the value of the wavefunction throughout the universe.

One alternative is to divide up the grounding task among the local entities (particles and/or Aristotelian substances). For instance, on a Bohmian story, one could divide up 3N-dimensional configuration space into N cells, one cell for each of the N particles, with each particle grounding the values of the wavefunction in its own cell. But it seems impossible to find a non-arbitrary way to divide up configuration space into such cells without massive overdetermination. (Perhaps the easiest way to think about the problem is to ask which particle gets to determine the value of the wavefunction in a small neighborhood of the current position in configuration space. They all intuitively have “equal rights” to it.)

It just seems neater to suppose a global entity to do the job.

A similar issue comes up in theories that require a global field, like an electromagnetic field or a gravitational field (even if these is to be identified with spacetime).

Here is another, rather different task for a global entity in an Aristotelian context. At many times in evolutionary history, new types of organisms have arisen, with new forms. For instance, from a dinosaur whose form did not require feathers, we got a dinosaur whose form did require feathers. Where did the new form come from? Or suppose that one day in the lab we synthesize something molecularily indistinguishable from a duck embryo. It is plausible to suppose that once it grows up, it will not only walk and quack like a duck, but it will be a duck. But where did it get its duck form from?

We could suppose that particles have a much more complex nature than the one that physics assigns to them, including the power to generate the forms of all possible organisms (or at least all possible non-personal organisms—there is at least theological reason to make that distinction). But it does not seem plausible to suppose that encoded in all the particles we have the forms of ducks, elephants, oak trees, and presumably a vast array of non-actual organisms. Also, it is somewhat difficult to see how the vast number of particles involved in the production of a duck embryo would “divide up” the task of producing a duck form. This is reminiscent of the problem of dividing up the wavefunction grounding among Bohmian particles.

I am now finding somewhat attractive the idea that a global entity carries the powers of producing a vast array of forms, so that if we synthesize something just like a duck embryo in the lab, the global entity makes it into a duck.

Of course, we could suppose the global entity to be God. But that may be too occasionalistic, and too much of a God-of-the-gaps solution. Moreover, we may want to be able to say that there is some kind of natural necessity in these productions of organisms.

We could suppose several global entities: a wavefunction, a spacetime, and a form-generator.

But we could also suppose them to be one entity that plays several roles. There are two main ways of doing this:

1. The global entity is the Universe, and all the local entities, like ducks and people and particles (if there are any), are parts of it or otherwise grounded in it. (This is Jonathan Schaffer’s holism.)

2. Local entities are ontologically independent of the global entity.

I rather like option (2). We might call this semi-holism.

But I don’t know if there is anything to be gained by supposing there to be one global entity rather than several.

Microphysics and philosophy of mind

Much (but not all) contemporary philosophy of mind is written as if microphysics were fundamental physics. But as far as I know, only on those interpretations of quantum mechanics that disallow indeterminacy as to the number of particles can microphysics be fundamental physics. The most prominent such interpretation is Bohmianism. On most other interpretations, the most we can say about the number of particles is that we are in a superposition between states with different numbers of particles. But reality has to have determinate numbers of fundamental entities. The picture of reality we get from both relativity theory and mainstream interpretations of quantum mechanics other than Bohmianism and its close cousins is that fundamental physical reality consists of global entities such as the spacetime manifold or the wavefunction of the universe rather than microscopic entities like particles. (I am attracted to a non-mainstream interpretation on which the fundamental physical entities may include mid-sized things like dogs and trees.)

Sometimes, pretending microphysics is fundamental physics is excusable. For certain discussions, it doesn’t matter what the fundamental physics is—the arguments work equally well for global and local fundamental entities. In other cases, all that matters is relative fundamentality. Thus, facts about chemistry might be held to be more fundamental relative to biology, and facts about microphysics might be fundamental relative to chemistry, even if the microphysics facts themselves are not fundamental simpliciter, being reducible, say, to facts about global fields.

But even when the arguments do not formally rely on fundamental physics being microphysics, it is risky in a field so reliant on intuition to let one’s intuitions be guided by acting as if fundamental physics were microphysics. And doing this is likely to mis-focus one’s critical attention, say focusing one more on the puzzle of why the functioning of various neurons produces a unified consciousness than on the puzzle of how the functioning of a handful of global entities results in the existence of billions of minded persons.

Perdurance and particles

A perdurantist who believes that particles are fundamental will typically think that the truly fundamental physical entities are instantaneous particle-slices.

But particles are not spatially localized, unless we interpret quantum mechanics in a Bohmian way. They are fuzzily spread over space. So particle-slices have the weird property that they are precisely temporally located—by definition of a slice—but spatially fuzzily spread out. Of course, it is not too surprising if fundamental reality is strange, but maybe the strangeness here should make one suspicious.

There is a second problem. According to special relativity, there are infinitely many spacelike hyperplanes through spacetime at a given point z of spacetime, corresponding to the infinitely many inertial frames of reference. If particles are spatially localized, this isn’t a problem: all of these hyperplanes slice a particle that is located at z into the same slice-at-z. But if the particles are spatially fuzzy, we have different slices corresponding to different hyperplanes. Any one family of slices seems sufficient to ground the properties of the full particle, but there are many families, so we have grounding overdetermination of a sort that seems to be evidence against the hypothesis that the slices are fundamental. (Compare Schaffer’s tiling requirement on the fundamental objects.)

A perdurantist who thinks the fundamental physical entities are fields has a similar problem.

A supersubstantialist perdurantist, who thinks that the fundamental entities are points of spacetime, doesn’t run into this problem. But that’s a really, really radical view.

An “Aristotelian” perdurantist who thinks that particles (or macroscopic entities) are ontologically prior to their slices also doesn’t have this problem.

Oligonism

Monism holds there is only one (or at least one fundamental) thing in reality: the universe. Pluralism, as normally taken, holds there are many. An underexplored metaphysical view is oligonism: the view that there are (at least fundamentally) only a handful of objects in reality, but more than one.

One way to get oligonism is to take the universe of monism and add God while holding that God is not derivative from the universe. But that’s still a monism about created reality, and my interest here is going to be in oligonism about created reality (the non-theist reader can substitute “concrete reality”).

The most promising version of oligonism is one on which the correct physics of the world consists of a handful of fundamental fields (e.g., gravitational, electromagnetic, etc.) and these fundamental fields are the fundamental objects in reality.

Oligonism suffers from an inconvenient complication as compared to monism. The monist can at least say that we have derivative existence as parts of a fundamental whole. The field oligonist cannot, because there is no one fundamental whole that we are parts of. On field oligonism, what we need to say is that each of us is jointly constituted by the arrangement of a handful of fields: I exist in virtue of the gravitational, electromagnetic and other fields having the right sorts of concentrations here.

Maybe, though, one can have one-many parthood relation: x is a part of y, z, w, ... even though x isn't a part of y, or z, or w, but only of all them jointly. Then we could exist as parts of the gravitational, electromagnetic and other fields, without us existing as parts of any one of them. A one-many parthood relation isn't crazy. Take an Aristotelian or van Inwagen view on which living things are the only complex objects. Now we could imagine two organisms, A and B, that each have a symbiotic relationship with a third object C but not with each other, so that we have two symbiotic wholes: AC and BC. Further suppose that only a part of C is involved in AC and a disjoint part of C is involved in BC. Then we could say that C is a part of AC and BC, but isn't a part of either AC or of BC, nor is there a greater whole ABC that contains all of C.

Of course, I don't think oligonism is true. The main reason I don't think that is that I think we are fundamental.

Aristotelian metaphysics and global physics

Too much of the contemporary ontological imagination is guided by the idea that the fundamental physical stuff in the world is discrete particles. Yet this is clearly dubious, since quantum mechanics (on non-Bohmian interpretations) suggests that the world is full of superpositions of states with different numbers of particles, while if discrete particles really exist, there had better be a well-defined number of them. Quantum mechanics instead suggests an ontology of the physical world where there is exactly one entity, “the Global Wavefunction”, whose physical state can be aptly represented as a vector in an infinite-dimensional vector space. And even if we didn’t have quantum mechanics’ vector-based approach on the table, we still wouldn’t be in an epistemic position to know that the right physics is based on particles rather than fields.

An ontology of material objects that composes these objects out of particles is held hostage to a particle-based physics that may well not be true. It would be best if one could work on the ontology of material objects without presupposing an answer to the question whether fundamental physical reality is field-like, vector-like or particle-like. I do not know if this is tenable. If it’s not, then the ontology of material objects needs to be done conditionally: If fundamental physical reality is of this sort, then material objects are like this.

Interestingly, some metaphysical problems may become easier given a non-particulate physical substratum. For instance, one of the hardest problems for a contemporary Aristotelian metaphysics has been the problem of what happens to particles that get incorporated into a substance, in light of the axiom that a substance cannot be composed of substances. But if we do not see fundamental physical reality as made of apparently substantial particles, the problem dissolves.

Today I want to sketch two Aristotelian approaches that take globalized vector- and field-approaches seriously. On the vector- and field-approaches, fundamental physical reality consists of a mere handful of entities: a single vector-like entity or several (hopefully no more than a dozen, and ideally only one) field-like entities. But being Aristotelian, we will think there are at least billions of substances: every organism is a substance. If these substances are to be related to fundamental physical entities, billions of them will have to be related to the same fundamental physical entities.

The ordinary substances on my stories will be organisms. There are billions of them. In addition to the ordinary substances, there are extraordinary substances: one for each of the handful of fundamental physical entities (fields or a vector).

My stories now diverge. On the first story, the billions of ordinary substances each encode and ground local features of the global fundamental physical entities. On a field version of the story, you encode and ground the features that the global fields have where you are located and your dog encodes and grounds the features that the global fields have where your dog is located (I am less clear on how to describe the vector version). This is not enough. For there aren’t enough organisms in the universe to ground all of the richness of the global fundamental physical entities: too much of the universe is lifeless. Thus, I propose that there are additional substances located where the organisms are not, and the features of these substances ground the rest of the features of the global fundamental physical entities. One way to run this story is to say that there is one of these additional substances per global fundamental physical entity, and each grounds the features of its corresponding global fundamental phsyical entity away from organisms. These additional substances are like swiss cheese, with the holes being filled with organisms like people and dogs.

On this version of the Aristotelian story—which can be varied in a number of ways—the global fundamental physical entities are not metaphysically fundamental. They are grounded in the many substances of the world.

On the second story, the global fundamental physical entities are substances. They are global substances. These global substances interact with the ordinary substances (there are many ways to spell out this interaction). We can now identify the matter of an ordinary substance x either with x’s powers and liabilities for interaction with the global substances or with the plurality of these global substances qua interacting with x.

There are many options here. Much detail to be worked out. Some options may be inferior to others, but I doubt in the end we will come to a single clearly best option.

Reductive accounts of matter

I’ve toyed with identifying materiality with spatiality (much as Descartes did). But here’s another very different reductive idea. Maybe to be material is to have energy. Energy on this view is a physical property, maybe a functional one and maybe a primitive one.

If this view is right, then one might have worlds where there are extended objects in space, but where there is no matter because the physics of these objects is one that doesn’t have room or need for energy.

Note that the sense of “matter” involved here is one on which fields, like the electromagnetic one, are material. I think that in the philosophical usage of “material” and “matter”, this is the right answer. If it turned out that our minds were identical with the electromagnetic fields in our brains, that would surely be a vindication of materialism rather than of dualism.

Now, here’s something I’m worrying about when I think about matter, at least after my rejection of Aristotelian matter. There seem to be multiple properties that are co-extensive with materiality in our world:

• spatiality

• energy

• subjection to the laws of physics (and here there are two variants: subjection to our laws of physics, and subjection to some laws of physics or other; the latter might be circular, though, because maybe “physics” is what governs matter?).

Identifying matter with one or more of them yields a different concept of materiality, with different answers to modal questions. And now I wonder if the question of what matter is is a substantive one or a merely verbal one? On the Aristotelian picture, it was clearly a substantive question. But apart from that picture, it’s looking more and more like a merely verbal question to me.

Particle accretion and excretion in Aristotelian ontology

In Aristotelian ontology the matter and parts of a substance get their being from their substance. But now we have a problem: we constantly accrete (say, when eating) and excrete (say, when sloughing off skin-cells) particles. These particles seem to exist outside of us, then they exist as part of us, and then one day they come to exist outside of us again. How could their being come from our form, when they existed before they joined up with us—sometimes, presumably, even before we existed at all?

But suppose an ontology for physics on which fields are more fundamental than particles, and particles are like a bump or wave-packet in a field. Then we have a very nice solution to the problem of accretion and excretion.

Imagine two ropes. Rope A is tied by one end to a hook on the wall and the other end of rope A is tied to the end of rope B. And you're holding the other end of rope B. You rapidly move your end of the rope up and down. A wave starts traveling along rope B, then over the knot, and finally along rope A. We are quite untroubled by this description of this ordinary phenomenon.

In particular, it is correct to say that the same wave was traveling along rope A as along rope B. Yet surely the being of a wave in a medium comes from the medium and its movement. So we have a very nice model. Rope A has excreted the wave and rope B has accreted the wave. (You might object that in Aristotelian ontology, ropes aren't substances. Very well: replace them with strings of living kelp.) If the knot is negligible enough, then the shape of the wave will seamlessly travel from rope A into rope B.

I think one reason an Aristotelian is apt to be untroubled by the description is because we don't take waves in a rope ontologically very seriously, just as we shouldn't take kings in chess very seriously. They're certainly not fundamental. Perhaps they don't really exist, but we have merely adopted a mode of speech on which it's correct to talk as if they existed.

However, if a field ontology is correct, we shouldn't take particles any more seriously than waves in a rope. And then we can start with the following model. Among the substances in the world, there are fields, gigantic objects that fill much of spacetime, such as the electromagnetic field. And there are also localized substances, which are tiny things like an elephant or a human or a bacterium. The fields have holes in them, holes perfectly filled by the localized substances. The localized substances exist within the fields much like a diver exists in the ocean—the diver exists in a kind of hole in the ocean's water.

Next, pretty much the same kinds of causal powers that are had by the fields are had by the localized substances. Thus, while strictly speaking there is no electromagnetic field where your body is found, you—i.e., the substance that is you—act causally just as the electromagnetic field would. A picture of the field you might have is of a string whose central piece had rotted out and was seamlessly replaced with a piece of living kelp that happened to have the same material properties as the surrounding string. But you don't just do duty for the electromagnetic field. You do duty for all the fundamental fields.

Because you have pretty much the same kinds of causal powers as the fields that surround you, waves can seamlessly pass through you, much as they can through a well-installed patch in a rubber sheet. You accrete the waves and then excrete them. Some wave packets we call "particles".

Objection: When I digest something, it becomes a part of me. But when a radio wave passes through me, it doesn't become a part of me even for a brief period of time.

Response 1: We shouldn't worry about this. In both cases we're talking about non-fundamental entities. There are many ways of talking. For practical reasons, it's useful to distinguish those wave packets that stick around for a long time from those that pass in and out. So we say that the former are denizens of us and the latter are visitors.

Response 2: Perhaps that's right. Maybe we don't exist in holes in the fields, but rather the fields overlap us. However, when the fields are in us, we take over some, but not all, of their causal powers. The radio wave that travels through me does so by virtue of the electromagnetic field's causal powers, while the particles of the piece of cheese that I digest and which eventually slough off with my dead skin travel through me by virtue of my causal powers. The picture now is more complicated.

Big or small?

Isn't it interesting that we are currently don't know whether the fundamental physical entities are the tiniest of things—particles—or the largest of things—fields—or both?

Substances and artefacts

Let us suppose that I am playing a nice game of Xiangqi with my daughter. The pieces are wooden, with painted red or black characters. As we play, we notice that one of the red catapult pieces has the character on its surface half warn off. So, I grab a laser pointer, and some motors, and a little processor, and program the motors to move the laser pointer rapidly so as to trace out the missing half of the character drawn on the piece, indeed to do so so rapidly that it looks like the character is all in place without any flicker. Moreover, I add a little camera that tracks the wooden disc, and continually repoints the whole assembly to follow the disc, so that when I move the disc, the character drawn on it moves with it. As we keep on playing (maybe the paint on the piece is of very low quality), more and more of the character wears off, and I am continually reprogramming the motors to replace more and more of the paint by the laser beam. Eventually, the disc has no paint on it, but has a laser image of the catapult character on it. I then take a bite out of the wooden disc itself. (Maybe I'm a beaver.) And I keep on taking more bites, while reprogramming the laser beam not to track what's left of the wooden disc, but to track my finger motions. Finally, I finish eating the wooden disc. I can now finish the game of Xiangqi with my daughter, except that now one of the red catapult pieces has become a pattern of laser light.

Suppose we were tempted to say that the initial red catapult piece was a substance.[note 1] Now, surely, a pattern of laser light isn't a substance. Light-spots aren't even processes, but quasi-processes. They can, after all, "move" faster than light.[note 2] So then we have the oddity that a substance became a non-substance. But it is plausible, for the same reasons for which it is plausible to suppose that the Ship of Theseus survives the replacement of its parts, that the red catapult piece survives its replacement with a light spot. Thus, if the red catapult piece initially was a substance, then one and the same thing is an existent substance at t₀ and an existent non-substance at t₁. Moreover, this didn't take any kind of miracle—all it took was a bit of skill with motors and electronics. If this seems absurd to you, then you may wish to conclude that the initial red catapult piece was not a substance.

Similarly, a painting could be restored with new paint, or it could be repaired piece by piece by projected light. A chair could be replaced, piece by piece, with force-fields, perhaps, or maybe even with carefully aimed jets of air. A computer could be replaced, piece by piece, with an emulation of itself (just replace the parts one-by-one with emulations). If these things survive this kind of replacement, and if we do not wish to accept that there can be change between categories—that a substance can change into a non-substance, say—at least without a miracle[note 3], then the conclusion to draw is that Xiangqi pieces (and by the same token international chess pieces), paintings, chairs and computers are not substances. In fact, it seems plausible to generalize this: perhaps no artefact is a substance, unless perhaps it is wholly composed of one non-artefactual substance (such as Peter van Inwagen's example of the hammock that is made out of one snake, weaved into a hammock like a rope).

Some of us want to go one step further, and deny that artefacts, except perhaps if wholly composed of one non-artefactual entity, exist. For it is not implausible to say that spots of light don't exist, and anything that can change into a spot of light doesn't exist either.

Progress report: naturalism and persons

This is just a progress report, a promissory note without much argument. I've been thinking a lot about naturalism and persons. Specifically, I've been thinking whether there is room for persons in a naturalistic ontology. One lemma that I've become convinced of is that if necessarily all persons are substances, so that if x is a person, then for x to exist is not a matter of something beyond x having some property or standing in some relation, then naturalism is false. In an earlier post, I gave an argument for this conclusion based on speculative physics, but now I am convinced that the conclusion holds independently of the speculative physics. Basically, the idea is that if naturalism holds, strong AI is true (it would be too weird if naturalism were true but minds had to be tied to a biology like ours), but if strong AI is true, then I suspect it is possible for a token computer program to be a person, and token computer programs are not substances (their existence is a matter of a computer having a particular state).

Moreover, it is plausible that finite persons are ontologically homogeneous: if one finite person is a substance, they all necessarily are. If this is correct, then if we are substances, naturalism is false.

Are persons substances? Are we substances? If we adopt an Aristotelian ontology, there are three alternatives to a person being a substance: she might be accident-like (e.g., a trope or a token relation), she might be the essence of a substance, or she might not exist. I take it that persons exist. The same kinds of thoughts that suggest that if naturalism holds, persons need not be substances, also suggest that if naturalism holds, then persons need not be essences of substances. So, on this kind of ontology, the question comes down to: Can persons be accident-like?

But consider the following thoughts: (a) if naturalism is true, then the best theory of personal identity will be a memory-based theory, (b) programs can seamlessly move between processors and even between computers, and (c) accident-like entities cannot move between substances. To me, these thoughts suggest that if naturalism holds, persons can't be accident-like, unless appearances are deceiving and moving from one body to another, or one computer to another, wouldn't involve a movement between substances. But the only way this could be is if the persons are accidents of some grand global substances, like the Cosmos, or Spacetime, or the Fields of a unified field theory.

Thus, assuming an ontology that has only substances and accident-like entities, the conclusion I draw is that if naturalism holds of persons, we are all modes (to use Spinozostic terminology) of one or more global substances. I doubt that on a sparse theory of properties and relations there will be enough modes to do the job. So the ontology will have to be one on which there are one or more global substances, of which everything else is a mode, and the modes are abundant. Moreover, since we have properties, this ontology will have to be one on which accident-like entities can be nested. I suspect that abundance will cause Unger-like problems with identifying who exactly we are, but I would like to have a better argument against such a Spinozistic ontology.

So this is where I am at right now in the argument: either some non-naturalistic account of persons is true, or a Spinozistic naturalistic ontology of one or more global substances, with nestable modes, probably abundant, holds. Of course I am convinced that the Spinozistic account is false (if only for ethical reasons: it doesn't do justice to the ethical importance of the body), but it would be nice to have a good ontological arguemnt here. With some modal imagination we might make progress: for instance we might think that even if in fact such an ontology holds, surely it would be possible to have persons apart from such an ontology, and this is enough to sink the naturalistic account. But I would rather not rely on modal imagination.

There is a lot of detail here that can be questioned. But the basic idea is, I think, sound: further progress on the question of whether the existence of persons is compatible with naturalism is going to be a matter not just of metaphysica specialis but of metaphysica generalis (i.e., of ontology).

An argument against materialism

1. The best physics tells us that material reality consists of one or more non-local fields. (Premise)
2. Therefore, material reality consists of one or more non-local fields. (Probabilistic inference from 1)
3. I do not consist of one or more non-local fields. (Premise)
4. I am a substance. (Premise)
5. A substance does not exist in virtue of one or more other things having certain properties. (Premise)
6. If x is a material entity, and material reality consists of one or more Fs, then x either consists of one or more Fs, or exists in virtue of one or more Fs having certain properties. (Premise)
7. I exist and have a mind. (Premise)
8. If I am a material entity, then I consist of one or more non-local fields, or exist in virtue of one or more non-local fields having certain properties. (By 2 and 6)
9. If I am a material entity, then I exist in virtue of one or more non-local having certain properties. (By 3 and 8)
10. If I am a material entity, then I am not a substance. (By 3, 5 and 9)
11. I am not a material entity. (By 4 and 10)
12. Therefore, I am an existent being who is not a material entity and yet has a mind. (By 7 and 11)