Physics and the Immortality of the Soul

[Cross-posted at Scientific American Blogs. Thanks to Bora Z. for the invitation.]

The topic of “Life after death” raises disreputable connotations of past-life regression and haunted houses, but there are a large number of people in the world who believe in some form of persistence of the individual soul after life ends. Clearly this is an important question, one of the most important ones we can possibly think of in terms of relevance to human life. If science has something to say about, we should all be interested in hearing.

Adam Frank thinks that science has nothing to say about it. He advocates being “firmly agnostic” on the question. (His coblogger Alva Noë resolutely disagrees.) I have an enormous respect for Adam; he’s a smart guy and a careful thinker. When we disagree it’s with the kind of respectful dialogue that should be a model for disagreeing with non-crazy people. But here he couldn’t be more wrong.

Adam claims that “simply is no controlled, experimental[ly] verifiable information” regarding life after death. By these standards, there is no controlled, experimentally verifiable information regarding whether the Moon is made of green cheese. Sure, we can take spectra of light reflecting from the Moon, and even send astronauts up there and bring samples back for analysis. But that’s only scratching the surface, as it were. What if the Moon is almost all green cheese, but is covered with a layer of dust a few meters thick? Can you really say that you know this isn’t true? Until you have actually examined every single cubic centimeter of the Moon’s interior, you don’t really have experimentally verifiable information, do you? So maybe agnosticism on the green-cheese issue is warranted. (Come up with all the information we actually do have about the Moon; I promise you I can fit it into the green-cheese hypothesis.)

Obviously this is completely crazy. Our conviction that green cheese makes up a negligible fraction of the Moon’s interior comes not from direct observation, but from the gross incompatibility of that idea with other things we think we know. Given what we do understand about rocks and planets and dairy products and the Solar System, it’s absurd to imagine that the Moon is made of green cheese. We know better.

We also know better for life after death, although people are much more reluctant to admit it. Admittedly, “direct” evidence one way or the other is hard to come by — all we have are a few legends and sketchy claims from unreliable witnesses with near-death experiences, plus a bucketload of wishful thinking. But surely it’s okay to take account of indirect evidence — namely, compatibility of the idea that some form of our individual soul survives death with other things we know about how the world works.

Claims that some form of consciousness persists after our bodies die and decay into their constituent atoms face one huge, insuperable obstacle: the laws of physics underlying everyday life are completely understood, and there’s no way within those laws to allow for the information stored in our brains to persist after we die. If you claim that some form of soul persists beyond death, what particles is that soul made of? What forces are holding it together? How does it interact with ordinary matter?

Everything we know about quantum field theory (QFT) says that there aren’t any sensible answers to these questions. Of course, everything we know about quantum field theory could be wrong. Also, the Moon could be made of green cheese.

Among advocates for life after death, nobody even tries to sit down and do the hard work of explaining how the basic physics of atoms and electrons would have to be altered in order for this to be true. If we tried, the fundamental absurdity of the task would quickly become evident.

Even if you don’t believe that human beings are “simply” collections of atoms evolving and interacting according to rules laid down in the Standard Model of particle physics, most people would grudgingly admit that atoms are part of who we are. If it’s really nothing but atoms and the known forces, there is clearly no way for the soul to survive death. Believing in life after death, to put it mildly, requires physics beyond the Standard Model. Most importantly, we need some way for that “new physics” to interact with the atoms that we do have.

Very roughly speaking, when most people think about an immaterial soul that persists after death, they have in mind some sort of blob of spirit energy that takes up residence near our brain, and drives around our body like a soccer mom driving an SUV. The questions are these: what form does that spirit energy take, and how does it interact with our ordinary atoms? Not only is new physics required, but dramatically new physics. Within QFT, there can’t be a new collection of “spirit particles” and “spirit forces” that interact with our regular atoms, because we would have detected them in existing experiments. Ockham’s razor is not on your side here, since you have to posit a completely new realm of reality obeying very different rules than the ones we know.

But let’s say you do that. How is the spirit energy supposed to interact with us? Here is the equation that tells us how electrons behave in the everyday world:

i\gamma^\mu \partial_\mu \psi_e - m \psi_e = ie\gamma^\mu A_\mu  \psi_e - \gamma^\mu\omega_\mu \psi_e .

Dont’ worry about the details; it’s the fact that the equation exists that matters, not its particular form. It’s the Dirac equation — the two terms on the left are roughly the velocity of the electron and its inertia — coupled to electromagnetism and gravity, the two terms on the right.

As far as every experiment ever done is concerned, this equation is the correct description of how electrons behave at everyday energies. It’s not a complete description; we haven’t included the weak nuclear force, or couplings to hypothetical particles like the Higgs boson. But that’s okay, since those are only important at high energies and/or short distances, very far from the regime of relevance to the human brain.

If you believe in an immaterial soul that interacts with our bodies, you need to believe that this equation is not right, even at everyday energies. There needs to be a new term (at minimum) on the right, representing how the soul interacts with electrons. (If that term doesn’t exist, electrons will just go on their way as if there weren’t any soul at all, and then what’s the point?) So any respectable scientist who took this idea seriously would be asking — what form does that interaction take? Is it local in spacetime? Does the soul respect gauge invariance and Lorentz invariance? Does the soul have a Hamiltonian? Do the interactions preserve unitarity and conservation of information?

Nobody ever asks these questions out loud, possibly because of how silly they sound. Once you start asking them, the choice you are faced with becomes clear: either overthrow everything we think we have learned about modern physics, or distrust the stew of religious accounts/unreliable testimony/wishful thinking that makes people believe in the possibility of life after death. It’s not a difficult decision, as scientific theory-choice goes.

We don’t choose theories in a vacuum. We are allowed — indeed, required — to ask how claims about how the world works fit in with other things we know about how the world works. I’ve been talking here like a particle physicist, but there’s an analogous line of reasoning that would come from evolutionary biology. Presumably amino acids and proteins don’t have souls that persist after death. What about viruses or bacteria? Where upon the chain of evolution from our monocellular ancestors to today did organisms stop being described purely as atoms interacting through gravity and electromagnetism, and develop an immaterial immortal soul?

There’s no reason to be agnostic about ideas that are dramatically incompatible with everything we know about modern science. Once we get over any reluctance to face reality on this issue, we can get down to the much more interesting questions of how human beings and consciousness really work.

  1. There is yet another line of reasoning, which is to note that the components of mind that people wish to contribute to an everlasting soul are themselves known to be conditional on material health of the human body. This is to say, presumably it is very important for the soul to have memory of the experiences of the body it inhabits (otherwise, how would it know whose soul it is? what would be the value of these experiences, and thus what is the purpose of the material life?). Yet we know that if we conk someone sufficiently hard on the head, or give them just the right drugs, or deny oxygen to part of the brain, that these things destroy memories and/or memory-making. People would also like to attribute personality to the soul, yet we know traumas like those described above can also change personality. And so on. Taken as individual components, I imagine there is evidence that every component of “mind” is dependent on material health of human body (brain). And yet people wish to believe that somehow taken together, they can transcend that.

  2. Nice food for thought. My only “complain” is that it seems that your arguments apply somehow also to consciousness. Please correct me if I’m wrong here but particles and interactions cannot explain life after death neither the consciousness of the human being. There’s a huge distance between equations and these topics… and this raises all the mystic about it (which is unfair, I hate it).

    I would like to see equations describing how particles interact to form our thought, and why we feel we are alive. Why a bunch of matter like us think ? I bet no one can present reasonable theories with equations on that. Yet, we are here having this healthy discussion… 🙂

    Its funny, because we may be a bunch of matter explaining matter.

  3. I mean…Nietzsche was saying God is dead nearly 150 years ago. This article quite literally gives a mathematical formula to that wider statement: modern civilization has no God, no religion, no Dante, no Sistine Chapel, as well as no Inquisition, no (religious) persecution. Our civilization is a civilization of science; it no longer needs God. God was there to provide the possibility of eternal life after death, and as was once put by a Spanish peasant “If there is no immorality, what’s the point of God?”

    Then again, I am only a philosophy major. My two cents of nonsense may or may not be worth anything.

  4. i also note that all of this discussion disallows for other dimensions, which are routinely discussed in physics. I think that to claim we know everything in this manner is to claim absolutely nothing. To say that the moon is demonstrably not made of green cheese, because we have physically analyzed it is extremely different from saying we have not demonstrated that there is a soul, simply because we haven’t shown that there is a dimension or particle or something that it is associated with.

    Which puts us back to the agnostic part.

  5. What do you think about the idea of quantum immortality/reincarnation in the MWI of quantum mechanics?

    The electrons in our brains are scattered in 99.99999…% of possible worlds but they reconstitute themselves in some way as a consciousness in 0.0000000…1% of them, and we get to live again, perhaps after a very long time and in a completely different place. A minimum “electron pattern” may persist, and when it “wakes up” again it may resembe someone who has amnesia + slept for years, but does preserve just enough of his old “self”. And, if the MWI is correct, then perhaps we (and some copies of ourselves), will only experience the small fraction of future worlds where our consciousness is reconstituted and is not scattered away.

  6. One thing I’m a bit ill-at-ease with you post, is that you’re discussing immortality of mind as if this belief was implicating belief in an unmaterial mind interacting with ordinary mater. Of course this is the most common belief, but maybe also the less interesting to discuss. What if one sees the mind as a program? Then mind is as immmortal as any equation in the Platonic heven, isn’t it?

    While I’m at it: suppose I say I understand how cars work, because cars are made of matter, and matter obbey QM, and I understand QM. Wouldn’t you think it’s a weak notion of understanding?

  7. One other thing not covered is non-local properties of mind. These have been demonstrated and written up on peer-reviewed journals for years. Do we know how that works? No, not yet. I’m not necessarily arguing for life after death, I’m just skeptical of claims that we know enough to answer the question. The history of science is the history of hubris.

  8. Quoting: “Within QFT, there can’t be a new collection of “spirit particles” and “spirit forces” that interact with our regular atoms, because we would have detected them in existing experiments.” Would we? Have we (really) detected dark matter, for instance? What about dark energy? I am NOT suggesting that a possible soul are made up of these two ‘things’!! But, as a friend of mine once said (when we were Physics students long ago): “I don’t think the laws of Physics are incorrect. But they may be incomplete.” Well, I’m quoting too much. Besides, a green cheese Moon would be cool…

  9. The general assumption — among physicists who believe in Christ, or Christians who believe in physics, or any combination of the two — is that the spacetime governed by the Standard Model is a subset of a more complete reality. Whether you want to use the extradimensional analogy of Flatland (the brain is to the soul as a cube is to a tesseract) or the computer science analogy (the brain is to the soul as the user input is to the user) or any other visualization, it isn’t that confusing.

    If the spacetime we know and see and test is but a tiny slice of a larger reality, and the larger reality only regularly interacts with ours in a few controlled ways (consciousness, etc), there is no reason to presume that we would be able to detect any portion of that reality that is necessarily located outside our own, any more than we would expect a computer program to be able to tell you anything more about its hardware components than the signals it is receiving from them.

  10. Quoting: “Within QFT, there can’t be a new collection of “spirit particles” and “spirit forces” that interact with our regular atoms, because we would have detected them in existing experiments.” Would we? Have we (really) detected dark matter, for instance? What about dark energy? I am NOT suggesting that a possible soul is made up of these two ‘things’!! But, as a friend of mine once said (when we were Physics students long ago): “I don’t think the laws of Physics are incorrect. But they may be incomplete.” Well, I’m quoting too much. Besides, a green cheese Moon would be cool…

  11. Re: #2 beteugelse:

    You raise a good point, but I think that the difference is related to the mind/matter connection. No one claims that consciousness is independent of matter. As #1 MPS17 says, physical encounters in the real world affect our mental and cognitive experiences. We certainly do not have a complete physical description of consciousness, but we do know that certain psychoactive drugs, brain injuries, and other physical stimuli have specific effects on consciousness. The difference is that for the soul, people claim that unlike consciousness, it maintains a separate existence that is somehow informed by, but not dependent on, the physical state of the body. We have admittedly imperfect ways of describing consciousness and its relation to the body that is not incompatible with physics – e.g. the whole field of neuroscience.

    We know consciousness ends at death because all of the neurological processes that we see impacting a person’s mental state, such as blood flow, cellular integrity, neural processing, end when the body dies. It therefore makes no sense to suppose that consciousness extends after death. If the soul survives death, it must not be composed of the ordinary matter that deteriorates. But in that case, we would have to explain how it was able to interact with the physical body in the first place, which brings forth the conflict with QFT.

  12. The persistence among certain commenters in insisting that consciousness CANNOT POSSIBLY be explained by current physics absolutely baffles me. I mean, yes, I’m sure consciousness is not fully understood or explained and is in much need of further investigation. So is Hox gene regulation and photosynthesis and the evolution of DNA. These–and consciousness–are all *biological* problems. Aside from the very general way that all physics relates to its emergent properties in biology, what is it about the problem of consciousness that makes people think it belongs in the realm of particle physics? I have never heard anyone argue that since there isn’t an “equation” for regulating the development of limbs in humans, we have to postulate entirely new laws of physics to explain how I’m typing this comment. There isn’t an “equation” for consciousness, but there’s still a very good, fits all the data, time-tested explanation for it and all other emergent phenomena of biology that have been shown to increase the fitness of our ancestors:


    Show me a good reason why consciousness can’t be a particularly spectacular result of the same overwhelmingly successful paradigm as EVERY OTHER ASPECT OF HUMAN BIOLOGY and maybe then it would be reasonable to start yammering at the particle physicists.

  13. @Beteugelse:

    Although there is much we don’t yet understand about consciousness, it seems fairly conclusive at this point that it is a product of electrochemical activity in the neurons of our brain. As such, consciousness does not require a mysterious particle or any fundamental change in our understanding of physics as does any life-after-death hypothesis. Said another way, consciousness does not seem to violate what we know to be true so long as it emerges from a living brain.

  14. @Alaya #12

    I don’t see anyone before your comment making this claim. The point is there is a difference between “current physics could explain conscisouness” and “current physics HAVE explained consciouness”.

    Current physics explains how cars work, but not because the behavior of small amount of matter is well explained by QM. 😉

  15. The green cheese argument is properly known as Ockham’s razor in philosophy of science. Essentially the argument points out that the data we have does not decisively point to a model where the moon is full of green cheese instead of one filled with ketchup or lego bricks. Therefore, a model where the moon is full of cheese is “needlessly complicated”.

    Similarly, one can enumerate many theories where a person has a soul that survives her, or has been reincarnated, or has two souls, or a soul shared by another living person, or a hierarchy of souls, or a soul that persists for only up to 100 years after the person’s death, or a soul only until the person stops believing it, etc. We don’t have data that definitely points to any of these theories and we may never have such data. The whole exercise is pointless.

  16. Let me preface my response with the fact that I am an atheist and have no religious or spiritual agenda for my response. But I would argue that the immortal soul may exist. We just keep answering the wrong questions. Every argument I’ve ever seen asks how ones consciousness can exist outside the body or after death. But no one stops to ask what is consciousness or why we even aknowledge it’s existence in the first place. Can anyone presume that they are the self creators of their own mater? What about the energy that causes the continous change in our bodies and leads to observable life? What about the information stored in ones brain? None of these originate from the individual, they flow in and through us and others as they have since the big bang. . So why do we assume that we exist at any given moment at all? I’ve seen argument that concsiousness is caused by neurological reactions, but aren’t those just responses to this same external stimuli? We put much weight on observation and perception, but as we know these are illusions of reality, extensions of the brains storage mechanisms, very human but not accurate representations of reality and very tied to external causation. Ultimately what I am suggesting is that the state of matter that we call body and mind are not the individual, but the changes that happen within and throughout, and these emanate from everywhere, each other and the universe, and as such are technically immortal. Fundamentally life is no different than non life, so maybe we should reexamine our understanding of ‘us’ and ‘I’, maybe consiousness and the soul is in the exchange, not the state being. We know that we cannot observe anything in our universe without change in state, so maybe the key to life is in that fundamental rule. I guess in the end we should examine more about what we are in the here and now before applying to much thought on the hereafter. Cheers.

  17. Occam Razor tells us that there must be a simple explanation and new physics does not exactly fit the bill. Then again 100% confidence raises alarm flags on my bullshit detector. What is your confidence interval on this claim?
    There are many paths to life after death that don’t require Casper or Ghost Buster dramatics. Most do “live” in the memory and behavior of others (and the fortunate ones live for very long) and that’s how haunted houses are made.
    Having said that I really wish I could filter out Sean’s post on philosophical themes (and movies also) 🙂

  18. Claims that some form of consciousness persists after our bodies die and decay into their constituent atoms face one huge, insuperable obstacle: the laws of physics underlying everyday life are completely understood, and there’s no way within those laws to allow for the information stored in our brains to persist after we die.

    But in an infinite multiverse, isn’t it likely that somewhere out there a pattern of information identical to our own brain’s last conscious experience will arise somewhere, and will survive to have additional experiences? This would seem especially natural in the many-worlds interpretation of quantum physics, leading to the theory of quantum immortality. Of course the question of whether “I” will experience such a branch of the multiverse depends on your assumptions of how continuity of consciousness/identity works, whether there is in fact any “objective” truth about the flow of consciousness in the first place (if not, then I can’t really even say that “I” will not be dead 10 seconds from now, replaced by a different brain state which just has memories resembling my experience)

  19. The actual configuration of atoms in your brain is one representation of the information that describes “who you are”. The equations that describe those states and interactions are another representation of that same information. Why can’t the “soul” just be another such representation of the same information? If it is, asking “How does the soul interact with the atoms of the brain” makes no more sense than asking “how does the quantum mechanical state vector for your brain (which given sufficient time and space I could write down on a piece of paper) interact with the atoms in your brain? It doesn’t, they are “in sync” because they represent the same information.

    To put it another way, my subjective experience of reading these words is not the same thing as the dynamics of my brain as I read these words. They are on some level “the same”, but I don’t consciously experience the act of reading as “Fire neuron 3141592, trigger synapse 2718281, etc.) Maybe one could be called “how my soul experiences it” and the other “how my brain experiences it.

    I suppose you could argue that that’s not what one normally means by “soul”, however. And I suppose you could say that if we define the soul as “just another representation of the information in the brain”, then it necessarily isn’t immortal. I’m not so sure that that’s the case, though — arguably the equations that represent the state of the brain in terms of underlying physics are immortal, in the “platonic ideal” sense in which all equations are (arguably) immortal.

  20. The soul doesn’t need to have an effect on our bodies to matter. If you have a problem with that concept, read “Permutation City” by Greg Egan… that’s the closest thing I can think of to a hard-science novel about the traditional idea of a “soul”.

  21. @Carol #4,

    To say that the moon is demonstrably not made of green cheese, because we have physically analyzed it

    …is not what the article says. We can infer that the moon is not made of green cheese even though we haven’t physically analyzed the interior, because of what we know about dairy produce and orbital bodies.

    In the same way, we can infer that there is no soul that persists after death because of what we know about physics. I don’t think extra dimensions help, since the soul would have to interact within the dimensions we know about.

    Of course, the usual route is to say that the soul exists in a non-material realm, implying that it interacts via non-material means, which is to say it happens by magic. We have a fairly good idea that things don’t work by magic, although a surprising number of adults still cling to the idea.

  22. As part of the choir being preached to, I seriously can’t see how arguing against the existence of an immortal soul using physical principles is supposed to persuade anyone except those who already reject the existence of an immortal soul. The green cheese analogy isn’t even relevant, because green cheese is not supernatural. How does the soul interact with ordinary matter? Why, the same way all supernatural influences are mediated. And because we are discussing the SUPERnatural, after all, violations of whatever symmetry or conservation law you wish to evoke are pretty much allowed by definition. You actually figure believers or “open-minded” agnostics feel the need to justify any of this? That some naturalistic foundation is even germane to the discussion? Logically, you’re rejecting any supernatural explanation from the outset, and then demanding a rebuttal to an argument the other side isn’t even making.

    There’s no debating these things. Such beliefs or suspicions are impervious to refutation by physics because they could be MIRACULOUS. That’s the whole damn point. Why bother?

  23. Well, there is soul and there is soul. The Advaita Vedantic theory is that awareness is part of the basic stuff of the universe. Not memory, not thought, not information, just awareness.

  24. Quantum mechanically speaking – no information is lost, ever; and so the whole of your life’s deeds and the accompanying information are (inextricably) entangled with the environment. Is this information retrievable? No. Does this entangled information form a sufficient basis for the Law of Karma to operate? Probably not, but don’t know for sure.

  25. The general assumption — among physicists who believe in Christ, or Christians who believe in physics, or any combination of the two — is that the spacetime governed by the Standard Model is a subset of a more complete reality.

    And the moon might really be green cheese, if we were to fully understand reality. But that fails parsimony, just as the assumption you mentioned.