The Core Theory and Strong Emergence

Responding to Sean Carroll's argument against everything

Sean Carroll, physicist and author of The Big Picture, has a go-to argument that works like a skeptical Swiss Army Knife. Whether your target is the soul, or the afterlife, or even psychokinesis, this one argument can do it all. It starts with a dramatic-sounding claim: The laws underlying the physics of everyday life are completely understood. He’s defended this claim in a series of blog posts, lectures, interviews, and published papers. There’s also a t-shirt. According to Dr. Carroll, this isn’t as ostentatious of a claim as it may sound at first. The macroscopic objects we interact with are composed of atoms and acted on by familiar forces, and we know how those particles and forces work. Sure, we don’t understand the full theory of quantum gravity, but we understand it perfectly well at the everyday level. In his blog post, “The world of everyday experience, in one equation”, he says, “No experiment ever done here on Earth has contradicted this model.” In another post, entitled “Seriously, the laws underlying the physics of everyday life really are completely understood”, he adds, “Electrons obey the same equations of motion whether they are in a rock or in a human heart.” 

The argument is relatively straightforward: You’re made of atoms. We know how atoms work. And atoms work the same way regardless of what larger structure they constitute. For that reason, there’s no room for anything beyond the materialism he advocates. We can discard any notion of an immaterial mind that’s causally connected to the body. Likewise, we can cast aside more radical parapsychological claims without the annoying business of investigating the subject too closely, since we already know it must be wrong. Carroll’s view seems to be that this argument, if successful, would rule out a raft of possibilities all at once. 

Of course, he recognizes that science is tentative, nothing is ever certain, and that there can be future revolutions in our understanding of nature. He’s not claiming to have ruled out anything with absolute certainty, nor is he claiming that physics is somehow complete. Not at all. Rather, the domain of physics relevant to everyday human life is well-established enough that we can say with a very high degree of confidence that there is nothing non-physical, paranormal, or supernatural at work in our world of protons, neutrons, and electrons. Dr. Carroll thinks we should conclude that the natural phenomena of our world, everything from brains to social systems, are entirely constituted and determined by the microphysical, given the empirical success of the Core Theory. Basically, if there were any forces, entities, etc. that exerted a causal impact on the everyday physical world of spoons and fleshy organisms, physicists would have found experimental evidence of their influence by now. According to Carroll, it’s completely implausible that “the laws of physics that have been tested by an enormous number of rigorous and high-precision experiments over the course of many years are plain wrong in some tangible macroscopic way, and nobody ever noticed.” Much more likely, he says, those who think they have something that contradicts the laws of physics relevant to everyday life have probably just done some careless research, fallen prey to confirmation bias, or trusted unreliable testimony. 

Watch on YouTube: Strong Emergence vs. The Core Theory (Response to Sean Carroll)

Here’s a summary of the argument from the abstract of Carroll’s paper, The Quantum Field Theory on Which the Everyday World Supervenes: 

Effective Field Theory (EFT) is the successful paradigm underlying modern theoretical physics, including the “Core Theory” of the Standard Model of particle physics plus Einstein’s general relativity. I will argue that EFT grants us a unique insight: each EFT model comes with a built-in specification of its domain of applicability. Hence, once a model is tested within some domain (of energies and interaction strengths), we can be confident that it will continue to be accurate within that domain. Currently, the Core Theory has been tested in regimes that include all of the energy scales relevant to the physics of everyday life (biology, chemistry, technology, etc.). Therefore, we have reason to be confident that the laws of physics underlying the phenomena of everyday life are completely known.

He uses this argument – I’ll call it the argument from the core theory – in a million different contexts, many of them related to consciousness. He uses it to argue against the afterlife, the soul, psychokinesis, levitation, panpsychism, and against far more specific philosophical views like the idea that rationally responding to one’s value judgments or conscious inclinations is a fundamental form of causation. Like I said, Swiss Army Knife. 

Lest I be accused of strawmanning, let me take one more stab at explaining the chain of reasoning here. Why do the defenders of the core theory argument think it rules out, say, an immaterial soul? Well, dualists typically believe that the soul has causal effects on the body. The body is made of atoms, which are made of protons, neutrons, and electrons. The dualist is telling us that atoms behave differently as a result of the influence of the soul. Imagine if we chose one of those subatomic particles to ignore completely in all our experiments. Our predictions wouldn’t pan out, since we’re ignoring a particle that exerts a causal influence on what we’re observing. And yet, this isn’t currently happening even though we are ignoring this influential soul-stuff. If we just removed any mention of protons from our standard model of the stuff that exists in our everyday world, what we observe in experiments would stop making sense because protons make a difference. Mental substance is supposedly a very physically influential substance! It makes a difference. You’d think there’d be some physical evidence for it!

Reply: Dualists only think mental substance makes a difference in certain macroscopic systems. Their view doesn’t predict that we would see its influence in the microphysical world when it’s not a part of those macroscopic systems. When was it ever part of the dualist view that the soul would influence the events in a particle accelerator? The idea that needs to be defended explicitly is that atoms behave the same way regardless of what larger system they constitute. That is what’s in dispute. In other words, what needs to be defended is micro-reductionism. 

On micro-reductionism, what a human being does is ultimately fixed by the fundamental particles making them up, and the behavior of the fundamental particles making them up is entirely determined by the basic laws of physics. As Carroll (2021) put it, “Electrons and other particles obey the same equations whether they are inside a rock or inside a human brain.” That is the crucial step, and it can’t be tested in a particle collider! If we’re trying to figure out whether atoms behave in the same way in microscopic and macroscopic systems, you can’t just test the microscopic systems. The micro-physical, in isolation, will behave identically whether or not there are novel causal principles that only arise at macroscopic levels of organization and complexity. As Ralph Stefan Weir put it on Twitter, “Looking in a particle accelerator for evidence against strong emergence in the brain is like looking under a lamppost for the key you lost on the other side of the street because that's where the light is.”

Weak Emergence 

We should note the important division Carroll makes between “weak emergence” and “strong emergence”. Weak emergence is compatible with (if not just another name for) reductionism, but strong emergence is anti-reductionist. (In philosophy, “strong emergence” is often just called “emergence”, but we’ll stick with Carroll’s slightly non-standard use of terms here.) As he said in 3AM Magazine, 

I think emergence is absolutely central to how naturalists should think about the world, and how we should find room for higher-level concepts from tables to free will in a way compatible with the scientific image. But “weak” emergence, not strong emergence. That is simply the idea that there are multiple theories/languages/vocabularies/ontologies that we can use to usefully describe the world, each appropriate at different levels of coarse-graining and precision. I always return to the example of thermodynamics (fluids, energy, pressure, entropy) and kinetic theory (collections of atoms and molecules with individual positions and momenta). Here we have two ways of talking, each perfectly valid within a domain of applicability, but with the domain of one theory (thermodynamics) living strictly inside the domain of the other (kinetic theory). Crucially, the “emergent” higher-level theory can exhibit features that you might naively think are ruled out by the lower-level rules; in particular, thermodynamics famously has an arrow of time defined by the Second Law (entropy increases in isolated systems), whereas the microscopic rules of the lower-level theory are completely time-symmetric and arrowless.

I think this example serves as a paradigm for how we can connect the manifest image to the scientific image. Sure, there’s nothing like “free will” anywhere to be found in the ultimate laws of physics. But that’s not the only question to ask; at the higher-level description, we should ask whether our best emergent theory of human beings includes the idea that they are (in the right circumstances) rational decision-making agents with freedom of action. Until we come up with a better description of human beings, I’m perfectly happy to say that free will is “real.” It’s not to be found in the most fundamental ontology, but it’s not incompatible with it either; it’s simply a crucial part of our best higher-level vocabulary.

In a future episode, I want to really dig more into the “poetic naturalism” defended in his book, The Big Picture, because it’s really interesting. For now, we just need to understand that strong emergence is not kosher, but weak emergence is central to Carroll’s worldview. As he puts it, “Little things can come together to make big things. And those big things can often be successfully described by an approximate theory that can be qualitatively different from the theory of the little things.” For example, an atom is just a collection of protons, neutrons, and electrons. Atoms emerge, in the weak sense. The language of “atoms” is a convenient way of talking about collections of protons, neutrons, and electrons. It’s the same stuff that was already there prior to the formation of the atom, so there’s been no ontological addition to the physical world when subatomic particles come together to make atoms. 

Strong Emergence 

Weakly emergent phenomena don’t involve anything “over and above” their constituent parts. Strongly emergent phenomena, by contrast, involve novel entities or forces or powers that arise at higher levels of complexity and organization, such that the new behaviors couldn’t be derived from the individual behaviors of the constituent parts of the system. As Philip Goff (2021) elaborates, strong emergentists

“believe that certain complex systems, such as conscious brains, have novel causal capacities that could not be predicted from knowledge of their basic components. Imagine a superintelligence, of the kind imagined by Laplace, who has total knowledge of the particles and fields covered by the Core Theory at time t, and tries to work out the state of my brain at t+1, solely on the basis of the Core Theory. If strong emergence is true, that superintelligence will make some false predictions about the locations of the particles in my brain at t+1, as it is relying entirely on the Core Theory and is ignorant regarding the contribution of the emergent causal capacities of my brain.” 

If you make an argument for micro-reductionism, you’ve made an argument against strong emergence. Carroll attempts an argument for micro-reductionism: the argument from the core theory. The problem with the argument is that the experimental evidence cited does not actually support micro-reductionism.

Strong emergence would work roughly like this: Natural laws, which exist in addition to the ones currently well-understood, describe novel entities or forces or powers or causal principles that apply at higher levels of complexity – but only at those higher levels of organization. Testing the lower levels of organization does nothing to cast doubt on the existence of these other natural laws, causal principles, etc. The microphysical would behave in the same way whether there was strong emergence or not. 

This is not some kind of ad hoc adjustment to the theory, tailored to dodge the evidence. It is just straight up not a part of the theory that the microphysical world being tested in particle colliders would behave differently as a consequence of laws that only apply to higher-order systems. If you thought this was some kind of knock-down argument, you misunderstood the emergentist position.

Avoiding the Many Perils of Modifying Physics 

It’s sometimes asserted that conservation of energy – that energy cannot be created or destroyed – rules out strong emergence, since strong emergence would be an example of the total amount of energy in a system spontaneously increasing. But as David Papinau (2002) explains, 

“[T]he conservation of energy in itself does not tell which basic forces operate in the physical universe. Are gravity and impact the only basic forces? What about electro-magnetism? Nuclear forces? And so on. Clearly the conservation of energy as such leaves it open exactly which basic forces exist.” 

So long as emergent mental forces “operate in such a way as to ‘pay back’ all the energy they ‘borrow’ and vice-versa”, Papinau argues, they have acted “conservatively”. Adding fundamental forces or causal principles does not mean violating conservation, nor does it imply that physics is wrong, strictly speaking. The laws underlying everyday life are true as far as they go — they’re just incomplete. 

Furthermore, Nancy Cartwright (1983) has argued that physical laws involve an implicit ceteris paribus clause: the laws of physics specify what will happen all things being equal. And in the cases we’ve been discussing, all things are not equal. If Cartwright is correct about the semantic point, then those who reject micro-reductionism are not really even departing from the predictions associated with quantum mechanics. But the emergentist case doesn’t hinge on this; those who reject materialist micro-reductionism could simply embrace the alternative. Supplementing or expanding the inventory of the natural world is a far cry from simply saying “physics is wrong”.

David Chalmers (1996) uses the analogy of electromagnetism to quell a few worries about modifying physics: 

“In a way, what is going on here with consciousness is analogous to what happened with electromagnetism in the nineteenth century. There had been an attempt to explain electromagnetic phenomena in terms of physical laws that were already understood, involving mechanical principles and the like, but this was unsuccessful. It turned out that to explain electromagnetic phenomena, features such as electromagnetic charge and electromagnetic forces had to be taken as fundamental, and Maxwell introduced new fundamental electromagnetic laws. Only this way could the phenomena be explained. In the same way, to explain consciousness, the features and laws of physical theory are not enough. For a theory of consciousness, new fundamental features and laws are needed. This view is entirely compatible with a contemporary scientific worldview, and is entirely naturalistic. On this view, the world still consists in a network of fundamental properties related by basic laws, and everything is to be ultimately explained in these terms. All that has happened is that the inventory of properties and laws has been expanded, as happened with Maxwell. Further, nothing about this view contradicts anything in physical theory; rather, it supplements that theory.” (The Conscious Mind, 127-128) 

The crux of the issue, to reiterate, is that the experimental evidence cited doesn’t get you within a mile of micro-reductionism. The experimental conditions in which we’ve tested the Core Theory do not include complex biological systems. So, contrary to what is often asserted, we have not been given empirical grounds to reject strong emergence in the brain. As Carroll himself admits, 

“Particle-physics experiments typically examine the interactions of just a few particles at a time, so new physical laws that only kick in for complex agglomerations of particles are not necessarily ruled out by data we currently have.” 

Surprisingly enough, in his 2021 reply to Goff in the Journal of Consciousness Studies, he concedes this crucial point which seems to undermine his entire case. Let’s read what he says in context, since it is such a major concession: 

“One is, of course, free to contemplate whatever extravagant deviations from contemporary physics one likes. Particle-physics experiments typically examine the interactions of just a few particles at a time, so new physical laws that only kick in for complex agglomerations of particles are not necessarily ruled out by data we currently have. It’s worth noting, however, how profound a departure such laws would represent. The most fundamental principle of QFT is locality: fields at any one point in space-time are only influenced by the values and derivatives of other fields at that same point, not the behaviour fields at other points. Modifying the dynamical equations in ways that were sensitive to the complexity of a configuration of surrounding particles would represent a dramatic overthrow of this principle.” 

This all seems a little bit less convincing than the slam-dunk the core theory argument is usually presented as. Besides, the worries about “modifying” physics are overblown, which was part of Chalmers’ point. We’re supplementing; we're adding to the inventory of nature to best explain the data. In the same article, Carroll also suggests a couple ways in which the Core Theory might be modified to allow for such a “dramatic overthrow” of locality! In other words, strong emergentists do not need to reject the Core Theory wholesale – they can instead accept an alternative version of the Core Theory that permits strong emergence. (Either way, the evidence cited offers zero empirical grounds to reject strong emergence.) As Goff (2021) put it in a reply to Carroll, 

“Carroll is right that the strong emergentist is obliged to do some serious theoretical work. But this theoretical work need not be conceived of as modifying the Core Theory, but rather as explaining how the causal capacities of strongly emergent wholes interact with the causal capacities of particles/fields to co-determine what will happen. Understanding strong emergence in this way gives us a response to Carroll’s novel argument that ‘based on purely physical grounds rather than consciousness-based motivations, our expectation that the laws of quantum field theory might break down in biological organisms would be very low indeed.’ Maybe so, but we should think of strong emergence not as quantum field theory breaking down but as a new neuro-biological theory kicking in. And the place to look for when emergent neurobiological principles kick is not physics but neurobiology. … People get very excited about brain scans, but in fact they are very low resolution. Each pixel of an fMRI image corresponds to 5.5 million neurons, between 2.2 and 5.5 x 1010 synapses, 22km of dendrites, and 220km of axons (Logothetsis 2008). We are only 70% of the way through putting together a complete connectome of a maggot’s brain, with its 10,000 neurons (Cobb 2020: 257). The idea that we know enough about the workings of the human brain with its 86 billion neurons to know whether or not its workings involve strong emergence is not credible.” 

Suppose a biologist discovers what she thinks is an indispensable law of biology. She takes it to be a strongly emergent law of nature, one that only applies to biological organisms. Why would anyone run to a particle accelerator to test that hypothesis? Strong emergence doesn’t lead us to expect any effects at lower levels of organization and complexity, so it doesn’t count as any evidence against the theory that we don’t see any effects at lower levels of organization and complexity. If there are strongly emergent laws of nature involving (e.g.) biology, then studying the microphysical world for their effects makes about as much sense as studying a rock formation. Surprisingly, Carroll seems to concede this point. 

In short, if you’re trying to provide evidential support for the Core Theory over a modified version of the core theory that doesn’t have the same constraints with respect to locality, you should appeal to evidence that one would expect on one hypothesis but not the other. The microphysical evidence cited counts as no evidence against a modified Core Theory, since we’d expect the microphysical to behave in the same way regardless of which theory turns out to be true. Here’s how it’s supposed to work: “On Hypothesis 1, we’d expect to see x, while on Hypothesis 2, we’d expect ~x.” But in this case, both H1 and H2 predict x! It makes no sense to cite x as uniquely supporting H1 over H2.

To be clear, the strong emergentist’s claim is not that new causal principles have nothing at all to say about the behavior of matter composed of protons, neutrons, and electrons. The claim is rather that these new causal principles have nothing to say about the behavior of protons, neutrons, and electrons in isolation or when they are otherwise not a part of a specific higher-order system, process, structure, etc.

If there are laws that only apply to macroscopic systems and processes, we have to actually investigate those macroscopic phenomena to discover them. I’m afraid there’s no shortcut here.

LINKS 

Strong Emergence vs. The Core Theory (Response to Sean Carroll)

Sean Carroll speaking to the Freedom From Religion Foundation

Philip Goff: Is physics different in the brain? https://www.youtube.com/live/wlyKdirhOa4?si=RRYXSUbW8As7sRLw

Papers: 

Carroll: Consciousness and the Laws of Physics (2021) https://philarchive.org/archive/CARCAT-33

Goff’s response to critics: https://philpapers.org/archive/GOFPCF.pdf

The Quantum Field Theory on Which the Everyday World Supervenes (2021) https://arxiv.org/abs/2101.07884

Relevant blog posts from Carroll: 

https://www.preposterousuniverse.com/blog/2013/01/04/the-world-of-everyday-experience-in-one-equation/

https://www.preposterousuniverse.com/blog/2010/09/23/the-laws-underlying-the-physics-of-everyday-life-are-completely-understood/

https://www.preposterousuniverse.com/blog/2010/09/29/seriously-the-laws-underlying-the-physics-of-everyday-life-really-are-completely-understood/

https://www.preposterousuniverse.com/blog/2010/10/01/one-last-stab/

https://www.preposterousuniverse.com/blog/2011/07/18/the-effective-field-theory-of-everyday-life-revisited/

https://www.preposterousuniverse.com/blog/2011/05/23/physics-and-the-immortality-of-the-soul/

https://www.preposterousuniverse.com/blog/2008/02/18/telekinesis-and-quantum-field-theory/