The Effective Field Theory of Everyday Life, Revisited

For some reason Nature News was inspired to tweet about my old blog post on Seriously, The Laws of Physics Underlying Everyday Life Are Completely Understood. Which I mentioned on Facebook, which led to an interesting comment, which I then mentioned on Google+… but now it’s substantive enough that I feel like I am neglecting our loyal blog readers! So here is a copy of my G+ comment, and a lament that I suck at proper use of the internet.

Not sure what brought this back to life. Like the Lord of the Rings, this is part of a trilogy; don’t miss the first installment, or the exciting conclusion.

As Michael Salem points out on an alternative social-media site (rhymes with “lacebook”), some of the resistance to this really quite unobjectionable claim comes from a lack of familiarity with the idea of a “range of validity” for a theory. We tend to think of scientific theories as “right” or “wrong,” which is hardly surprising. But not correct! Theories can be “right” within a certain regime, and useless outside that regime. Newtonian gravity is perfectly good if you want to fly a rocket to the Moon. But you need to toss it out and use general relativity (which has a wider range of validity) if you want to talk about black holes. And you have to toss out GR and use quantum gravity if you want to talk about the birth of the universe.

Just because there is something we don’t understand about some phenomenon (superconductivity, cancer, consciousness) does not imply that everything we think we know might be wrong. Sometimes we can say with confidence that certain things are known, even when other things are not.

Not only do theories have ranges of validity, but in some cases (as with the Standard Model of particle physics) we know what the range is. Or at least, we know where we have tested the theory and where we can be confident it is valid. The Standard Model is valid for all the particles and interactions that constitute our everyday existence.

Today we think of ourselves and the stuff we see around us as made of electrons, protons, and neutrons, interacting through gravity, electromagnetism, and the nuclear forces. A thousand years from now, we will still think precisely that. Unless we destroy the planet, or are uploaded into computers and decide that the laws of physics outside the Matrix aren’t that interesting any more.

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72 Responses to The Effective Field Theory of Everyday Life, Revisited

  1. Jean Spoto says:

    The universe is interesting for containing emergence and phase transitions. Perturbative physics fails outside its interval. As with economics, mensicus and continuous fluid are two extremes of bottle washing and button sorting. Critical opalescense is the big ride! Scintillate, for the universe wants to be explained.

    You cannot manage discovery, you can only manage to end it. Imagination is intelligence having fun. Mourn the dead, fix the problem, and get on with the job.

  2. jpd says:

    ok, except that a proton isn’t a proton, its three quarks.

  3. Julien says:

    Our everyday existence includes consciouness, and we have no idea whether our “effective field theory of everyday life” can explain it. The problem is not that we do not understand it all. The problem is we may come to understand behavior without gaining any understanding of counsciousness. That makes this hard problem very different from, say, superconditivity and cancer.

  4. Georg says:

    “”Like the Lord of the Rings, this is part of a trilogy; “”

    Any good trilogy has a forth, maybe fith part,
    eg the Hitchhikers Guide…..

  5. Moshe says:

    I am late for all that, but I am confused about the precise statement. My confusion is that you are not making claims about the EFT relevant to everyday life’s scales, but on that “underlying” it, and I am not sure what makes an EFT “underlie” another one. Do you mean that we have a complete understanding of the effective field theory in distance scales just below that of those relevant to daily life? why is that a privileged length scale? In other words, in what way are we “made of” protons instead of quarks?

    Hard to make prediction for the far future, but FWIW: one possibility for how we describe things around us a thousand years is that we may have a different idea of what “things are made of” means, we may not even be using that language anymore. In strongly coupled QFTs it is already very hard to make precise this Russian doll picture of bigger things made of smaller ones. In different physical regimes you have different excitations, some small and some large, and there is no universal way in which some of them are “made of” others. The EFT relevant for each physical regime is unambiguous, but that “underlying” it may not be. Again, hard to make predictions but this is one way in which our description of the physics underlying everyday life can fundamentally change in the future.

  6. Low Math, Meekly Interacting says:

    “Underlying” is a crucial qualifier. Seems impossible, though, to avoid the debate about the existence of other “fundamental” laws of emergent phenomena not reducible to the SM and relativity. I tend to be highly doubtful that any such fundamental laws are there to be discovered, but am less sure the matter is resolved. Hence, I’m not sure there is no controversy. It may be mistaken controversy, but, as of yet, it seems impossible to say with much certainty one way or the other.

  7. Sean says:

    jpd– The fact that protons are made of quarks does not mean that protons do not exist. And what protons are made of is completely irrelevant to our everyday life.

    Julien– There is zero evidence that consciousness involves physics beyond the Standard Model. That doesn’t mean that it certainly doesn’t, but the evidence in favor of quantum field theory as it is understood is so overwhelming that you need to do much better than point to something complicated and say “well explain that.”

    Moshe– We could argue about the precise definition of the “everyday life regime,” but I doubt that would be much fun or very enlightening. Regardless, I feel confident that the effective theory of atomic nuclei plus electrons interacting via gravity and E&M is sufficient to account for what a reasonable person would judge to be “everyday life.” The point is that it doesn’t matter what lies beneath. There is no question you can ask about everyday phenomena that cannot in principle be addressed within that theory.

    LMMI– The known laws are mathematically complete; either they are incorrect, or they suffice to say we understand what underlies everyday life. There can also be emergent laws that are fascinating in their own right, but that is not an incompatibility with the underlying description.

  8. jpd says:

    the fact that protons exist is irrelevant to 99% of the population of the planet

  9. Low Math, Meekly Interacting says:

    OK, I see the distinction when put in those terms.

  10. rob says:

    sure Sean, but WWDCS?

    (what would deepak chopra say?)

    p.s. good post. i liked rereading your older trilogy too.

  11. Julien says:

    >you need to do much better than point to something complicated and say “well explain that.”

    Sean, my post was precisely to point that the hard problem of consciousness is not of the “well explain that” kind. Did you take some time to read the link? Another one:

  12. Moshe says:

    Sean, I was trying to make a different point, related to the imprecise nature of the word “underlying”, not that of “everyday life”. To give an analogy: is the physics underlying the quark-gluon plasma that of quarks and gluons interacting via the QCD lagrangian (which is in principle the complete story but in practice not all that useful), or is it that of 5 dimensional black hole in asymptotically AdS space?

    I would say that neither, or both, and in any case “underlying” in that context is not a very precise, unique or ultimately useful concept. Same may well hold for everyday phenomena that are “in principle” described by your effective field theory.

  13. Lord says:

    Until we discover wormholes permeate our everyday life without our knowing about it.

  14. Physicalist says:

    @ Julien:

    The “hard problem of consciousness” is based on philosophical confusion and gives us no reason to question the sort of physicalism that Sean is advocating. Philosophers just need to get a better understanding of what’s involved with understanding.

    Likewise, the common intuition that (phenomenological) zombies are possible is based a failure to conceive of all relevant physical facts. The arguments against physicalism just don’t hold up.

  15. nick herbert says:

    “[Before one can apply quantum theory] the existence and general nature of macroscopic bodies and systems IS ASSUMED AT THE OUTSET. These facts are logically prior to the interpretation and are not expected to find an explanation in it”–Wendall Furry on the measurement.

    If Sean claims that quantum theory can “explain the world” when it has to assume “the existence and general nature of macroscopic bodies” is to really stretch the meaning of the word “explain”.

    Until physicists can come up with a convincing narrative about what happens in a measurement, quantum mechanics may be a useful tool but it does not “explain the world” on any scale.

  16. Physicalist says:

    quantum mechanics may be a useful tool but it does not “explain the world” on any scale.

    Quantum mechanics explains the stability of atoms and molecules regardless of one’s interpretation of QM or one’s solution to the measurement problem.

    The predictive/formal accuracy of QM is enough for us to say that we have in hand the physics that is relevant for all neural processes. We therefore have very good evidence that all mental states are physical.

  17. Julien says:


    Always glad to learn something. Please let me know where I’m wrong:

    If consciousness can in principle be explained by some EFT, then computationalism is right (we can describe ourselves as binary vectors, got uploaded in some Matrix, etc). If that’s true, as I also tend to think, then all we can do could be done in principle using a coin and a lot of chance. This coin tossing, I call it a philosophical zombie. Don’t you?

    The point is, if philosophical zombies are possibles in principle, then we have the problem of deciding what computation is or is not conscious, and this is hard because we can’t rely on behavior.

  18. Loki says:

    Sean, i have a question to you
    You often remark that we don’t have any idea how consciousness works, that this problem is probably beyond our current methods and such. This is puzzling. You either didn’t read the literature on the subject, serious researchers and philosophers like Dennett, Ramachandran, Pinker, Mynsky etc. (An excellent book “Consciosness Explained” by a prominent 100% materialist philosopher Dennett is 20 years old!). Or you did read, but find all their models and arguments not just unconvincing but kind of empty ..

  19. Sean says:

    Moshe– There are certainly interesting questions of principle here, but I don’t see how they are relevant to this claim in practice. By “the laws of physics underlying everyday life” I mean “the theory of nuclei and electrons interacting via E&M and gravity.” Maybe there is some other dual description of that physics, but even if so it wouldn’t change the claim. As long as there is one description that works, we’re okay. Unless you are suggesting that there are some everyday phenomena that really don’t fit into that description because of some subtle nonlocalities or strong-coupling issues.

  20. Physicalist says:

    @ Julien

    Computationalism about the mental may or may not be correct, but it does not follow directly from physicalism. Physicalism (at the level of EFT) says that anything that is *physically* identical to you will also be identical with respect to its mental properties.

    However, a Matrix-computer process is not physically identical to the complex system of carbon, hydrogen, oxygen (etc.) atoms that is your brain.

    Philosophical zombies are not possible in principle. Physics is not only about behavior, it is also about the *causes* of behavior — specifically the forces, charges, and laws that *produce* behavior. The reason many philosophers erroneously believe that zombies are possible is that they conceive of physical behavior, but they don’t take proper account of the causes of behavior.

    Look at it this way:
    a) A physically identical world has to be causally identical to this world.
    b) Our conscious experiences (qualia) cause some behavior (my saying “ouch”).
    c) So any physically identical world has to include that cause; there has to be a conscious experience there; there cannot be a zombie.
    d) When you *think* you’re imagining a zombie, you’re really imagining a being that behaves like you, but that does not have the same causal-dynamical features that you have. So you’re not imagining a physically identical being.

  21. Loki says:

    Julien. i think the answer to your question is in the old say: “If it looks like a cow and moos like a cow, than it is probably a cow”. If there is no way to find a difference between a zombie and a “conscious” human – than zombie is a conscious human. We are incredibly complex biological machines and consciousness is an emergent phenomenon. As Dennett puts it: “- Yes, we have a soul. And it is made of thousands of tiny simple robots.”
    It’s like color vision – you have no doubt about your color 3D vision, right? Yet is is easy to check with just a deck of cards that what you actually see in color (and any decent detail) is dime-sized spot right ahead. All the colorful world around is a creation of small and fast automatic modules in your brain that you have no conscious access to.
    Same with consciousness. Lots of small modules work incessantly. Some on higher level formulate phrases and an urge to speak out ir write in this chat. All demand attention. The one that has the most strong signal at the moment gets attention of others, and so on. Imagine a big crowd of people on the town square. Some are silent, some murmur to the neighbours, some shout. What you feel like “You”, is not an observer of this crowd, but the most loud person at any particular moment!

  22. Moshe says:

    I think we both agree about the facts, but I an a bit uncomfortable with the language which seems stronger than the claim one can make. One can certainly envision a scenario where the best description of some everyday phenomena involves microscopic ingredients and mechanisms currently unknown, especially if the current ingredients become strongly coupled at the relevant physical regime. Even if such future description is consistent in principle with the current one, I suspect future physicists would claim the simpler description “underlies” that particular everyday phenomena, if they still use that language.

  23. Julien says:


    1) I did not say computationnalism follows from physicalism. I said computationnalism must follow from current EFT (from QM, in fact).

    2) it seems your vision of physicalism is non standard. More precisely, it does not includes supervenience: the fact that two pictures can be be identical despite not physically identical. Was it for clarity purpose?

    3) there are several evidences that most of the time you say “ouch” before your brain construct the conscious interpretation that you decided to say “ouch”.

    4) your right I’m extending the philosophical zombie notion to something that present identical behavior, not physically identical being. So I’m not arguing against physicalism, I’m arguing against the idea that we can have a great confidence that ” The Laws of Physics Underlying Everyday Life Are Completely Understood.”

    @ Loki

    “If it looks like a cow and moos like a cow, than it is probably a cow”

    Well said. 😉

    So, will you accept to provide citizenship to any computer program that statistically can’t be differentiated from a significant proportion of humans, or will you restrict it to the computer programs whose inner computations are closes enough to the human way?

  24. Physicalist says:

    @ Moshe

    What sort of strong coupling of current ingredients do you have in mind, and how would it undermine any of Sean’s claims? Are you suggesting that such couplings might occur in brain processes? Or are you just pointing out that if you slam together two electrons hard enough then current physics can’t predict what will happen?

  25. Physicalist says:

    @ Julien,

    1. I don’t see that computationalism follows from EFT. I’m not even sure what this would mean. What sort of computationalism are we talking about?

    2. By physicalism I do mean that all facts supervene on the physical facts. This means that if the physical facts are the same, then all other facts are the same also (which is what I tried to say above).

    3. Yes, I often say “ouch” before the qualitative feeling of pain really sets it. Which is why when I’m being careful, I instead talk about the action of my carefully and deliberatively describing a pain. In this case it seems clear to me that the feeling itself is playing a crucial causal role. I was trying to be brief in making my point that experiences obviously have physical effects.

    4. But once we accept physicalism, it seems that arguments about zombies and the so-called hard problem are completely irrelevant to the question of whether we understand the physics underlying life and cognition. For this question, the relevant points are the ones that Sean rightly points to: We know the domain of applicability of QED and Newtonian Gravity, and life and cognition are processes that lie safely within those domains.