# 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.

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### 198 Responses to Physics and the Immortality of the Soul

1. Cristi says:

I think your arguments should be improved. Maybe people believing paranormal stuff avoid scientific evidence and logic and prefer to commit fallacies. They rely on anecdotal experience and generalize with too much ease. But if we want to do better, we need to rely on science and logic better than they do. After all, scientists are not guided by wishful thinking, and they are agnostic until the evidence is provided.

1. “all we have are a few legends and sketchy claims from unreliable witnesses with near-death experiences”.

It would be nice if you can point a study, which was repeated and corroborated, and peer-reviewed, showing that people witnessing near-death experiences are unreliable. I hope the definition of “unreliable” is other than unreliable = people claiming to have such experiences.

2. The moon made of green cheese argument. This argument can have many other uses. It could have been used in the XIXth century to prove that it is impossible to have planes, or that there are no rocks in the sky. We can use it today against theories in physics which cannot be verified (yet), like string theory, multiverse theories, huge fluctuations of entropy.

3. “there’s no way within those laws to allow for the information stored in our brains to persist after we die”

This argument is able to defeat the straw-man who claims that the soul is a continuation/survival of the functions and memory of the brain. But can it be improved so that it defeats the following hypothesis about the soul?

What if the soul resides somewhere outside the physical universe (this is what they claim), and the information in the brain grows under the guidance of this soul? The information in the brain is not the soul, but it is somehow a projection of that in the soul. Consider the soul as a hard disk, and our universe as the RAM of the computer. The information from the soul is loaded into the RAM (a human body is born), and then, until the program is ended (the human body dies), some of the information gained while the program was running is saved back on the disk.

Now I don’t say that this is the truth, I just say that your argument should not reduce all the claims about the soul to the most easy to dismiss version.

4. “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.”

Well, this equation or something like this is true and it described how everything evolves, given the initial data. And clearly there is no “soul term” in the evolution equation.

But again, we can, if we want, make a “green-cheese hypothesis”:

Those reporting NDE and OBE claim that during such experiences they transcended time. If the soul is from “outside” our universe, then it has no reason to be prisoner of our time line. What if it can choose the initial data at t_0 to obtain the desired result at t_1? What if the soul does not affect the evolution equation with a term, but simply the initial conditions? The equation can be deterministic, but the soul can act by choosing the initial conditions.

You may say that there is no way you can change the initial conditions. I agree that we cannot change them, but what if they are not yet decided completely? Think how we can perform a delayed choice experiment and choose how a photon went from a distant galaxy towards us billions of years ago. What if quantum mechanics actually tells us that the initial conditions are not selected completely, and by choosing the observable we want to measure, we add information about the initial data? If this is so, then it can provide a way by which something outside our universe can influence what happens within our universe.

I don’t say that this is true. What I say is that you did not rule this possibility out. Of course, you may say that you don’t need, and go back to the green cheese moon argument. I hope you will not do this, because it will mean that this is your last argument. Now you may say that it is trendy to claim that quantum mechanics supports paranormal stuff. It may be so, and maybe quantum mechanics is abused in this way, but if one claims we should not be agnostic, one has to explain away the possibility that quantum mechanics offers support for “weird” stuff. To reject the agnostic position, one has to explain why it is OK to teleport the state of an electron into the past, but not to use the initial conditions of the universe to implement free-will and a way for the outer soul to act in the universe.

It’s interesting to know that information might be somehow be distinct from energy. If true, it might make possible, not only a new generation of memory devices, but an entirely novel theory of computing. I’d bet that nobody has a clue as to how to make it work, though.

3. piscator says:

There’s no evidence for a mortal soul either. And based on physics alone I have no reason to think that Sean Carroll is any different than a more complicated bit of rock – its just another N-body problem interacting according to the Schrodinger equation.

The difficulty with arguing against an immortal soul is that most arguments (this one included) also rule out a mortal soul. You establish that something meaningfully called ‘mind’ is a fiction after death, at the cost of establishing that it is also a fiction before death.

4. slw says:

To clarify my last comment, “and there’s no way within those laws to allow for the information stored in our brains to persist after we die” is the proposition I completely disagree with.
Yeah, we can’t do it yet, however I see no physical reason why a complete dump of the brain would not be possible. And if you can read it, you can copy it.
So the question of afterlife simply becomes “is there an innate process in nature that copies the informational content of the brain after it expires to some other storage?”, to which the most likely answer is “no”. However, in the future, we might very well be able to build such a machine ourselves.

5. WL says:

What is often neglected in after-life discussions is that the hard wiring of our brain determines our personality, the way we think and we perceice things. The “me” is firmly encoded in our specific neuronal substrate, which continually changes and it also depends on the chemical, hormonal climate of the moment. Just eat a certain drug or have a little stroke and you’d be a different person than yesterday.

So, what aspects of us are preserved in the soul when we die? Is it like a snapshot of the brain state in the moment of death?

If so, what is if we sleep at that time.. do we wake up when we die? If a blind person dies, can the soul suddenly see again? And if yes, what kind of colors can it see? What is the resolution, can it see atoms? Can the soul see in the dark? Does the soul of an Alzheimer patient suddenly become smart again? If you are drunk or depressive in the moment of death, in what state your after-life conciousness should be in? Actually 95% of all brain processes run unconciously but still influence our deeds and thinking… it is known that decisions are taken before we conciously know about them. How would that be encoded in a thinking soul?

If you say, well the soul is immaterial and these questions do not make sense, then what properties of your personality are preserved at all? At best this can be some vague feeling of existence and conciousness, but that could hardly be called “you”, who is a product of your specific history in the physical world.

6. Chaz says:

Lucid as always, Sean!

7. The average over comments give a good view about prevailing more than century old prejudices called for some reason “scientific view”, which is nothing but extremely naive materialism neglecting all its problems raised by modern physics itself (quantum measurement theory). Even the questioning of the belief that biology reduces to physics as we understand and that free will might be something real is regarded as a belief in paranormal! God grief!

The first thing that should be done to cure the situation would be inclusion of a course about basic unsolved problems related to consciousness to the basic curriculum in theoretical physics. Its scandalous that people who get so fantastic tools for problem solving are completely unaware about fundamental unsolved problems of consciousness and continue to repeat centuries old platitudes of materialism. For God’s sake: wake up! : we are not living times of French revolution anymore.

8. jumbo says:

Alaya, you are saying:

“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”

I think there are some empirical INDICATIONS that conciousness may survive death. One set of related data is coming from research of NDE (for a 2010 update see e.g. Evidence of the Afterlife: The Science of Near-Death Experiences by Jeffrey Long and Paul Perry).
Another set of interesting data was produced over several decades at the University of Virginia, where they study “Children’s memories of Previous Lives” (for a 2005 summary see e.g J. B. Tucker, Life before life). In fact I believe that in case of less controversial results, the proofs given in these two fields would be already considered sufficient, but extraordinary claims require extraordinary proofs…….

I am sometimes asking myself why physicists can freely discuss some never (so far) detected phenomena such as dark matter (hopefully to be detected soon), extra spacelike dimensions (do they really exist?), multiverse (is this even measurable in principle?) and not other phenomena (soul, NDE etc).

9. jumbo says:

Alaya, you are saying:

“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”

I think there are some empirical INDICATIONS that conciousness may survive death. One set of related data is coming from research of NDE (for a 2010 update see e.g. Evidence of the Afterlife: The Science of Near-Death Experiences by Jeffrey Long and Paul Perry).
Another set of interesting data was produced over several decades at the University of Virginia, where they study “Children’s memories of Previous Lives” (for a 2005 summary see e.g J. B. Tucker, Life before life). In fact I believe that in case of less controversial results, the proofs given in these two fields would be already considered sufficient, but extraordinary claims require extraordinary evidence…….

I am sometimes asking myself why physicists can freely discuss some never (so far) detected phenomena such as dark matter (hopefully to be detected soon), extra spacelike dimensions (do they really exist?), multiverse (is this even measurable in principle?) and not other phenomena (soul, NDE etc).

10. Cristi says:

The Moon is a coagulation in our galaxy, Milky Way. Milky Way is made, like any other galaxy, of milk. Why else would scientists call the galaxies “galaxies” (gala=milk)? Therefore, the Moon is made of cheese. Now considering the age of the Moon, obviously the cheese turned green. QED.

11. David George says:

“Of course, everything we know about quantum field theory could be wrong. Also, the Moon could be made of green cheese.”

The relevant question here is not whether what is known about quantum field theory is wrong. Quantum field theory is a human invention. How could the inventors not know about their own invention? The question is, does quantum field theory describe physical reality? And more importantly, does quantum field theory explain all the elements of physical reality? I do not believe anyone can claim that. Some things that quantum field theory “knows” about physical reality could be wrong. For example, an effect must always lie in the future relative to its cause, according to currently understood theory. However it is not possible to determine whether a signal arrives at any location from the past or from the future. The choice of designation is arbitrary. If a universal signal arrives at every universal location from the future, it cannot be located in physical reality (try to find it) and yet it influences physical reality. And there must be some delay between the source and the receiver, and this delay must also lie in the future relative to the reception. The question then is, is retrograde signalling possible?

12. Doug Warren says:

A loose interpretation of Godel’s incompleteness theorem might be that you can neither prove nor disprove the existence of anything outside of a closed system from within that closed system. Prove or disprove God? Not from our frame of reference. Closer to our culture, I can imagine that any experiment you could do in the Matrix would come out as you expect it to. Doesn’t prove that your world is “real”. Come to think of it, maybe it’s not. Solid? No, you’re almost entirely empty space! And what is “there” is only a pattern of “energy” that persists very briefly. So when you start looking at science, you quickly see we’re all living in a fairy tail anyway. We’re still soooo very primitive. Be humble and find joy in the wonder.

13. Luis says:

If I may quote Dr. House,

Rational arguments don’t work with religious people; if they did, there wouldn’t be any religious people.

So: you are right, but blog posts like this one are largely exercises in futility.

14. beteugelse says:

Thanks for the reply. Well explained. Thats a good way to go, indeed.

Should we REALLY abandon the idea of life after death given the standard models and the known interactions (please say yes!) ? Of course such research could be a road to nothing, like search for green cheese on the Moon… but this would be of great interest to humanity. Can you imagine a nice paper showing that ? It would be nice to end with religion, right ?

The problem is: we don’t have a published paper saying that a soul does not exist. And we don’t have more papers confirming that either. Thus, in this case, it is still not a “scientific truth”, that is, religious people can always say that science did not handle this problem. Perhaps there’s an exotic field, blah blah.

To conclude. The subject and tools we have at hand are disparate. This a bar topic, with beer.

15. TedL says:

Sean,

I enjoyed your post. But I find it hard to get worked up about what other people choose to believe. I don’t believe in god or the afterlife; I’m not trying to amass points on the Cosmic Scorecare for being “right” on the issue. The answers that science provides are readily available to those who are interested. But I think religions are shaped by tradition, culture, and experience — which, dogma aside, can make religion a good thing. Regardless, I find that religion/god/afterlife have a miniscule affect on my daily life.

Thanks for a great blog entry. It went quite well with my Konga Yirgacheffe coffee, brewed in a french press. If it were evening, I probably would have been sipping a tasty home brew–dry hopped for a refreshing bitterness. Some might find those choices repulsive. We can all weigh in on what we like and why. C’est la vie.

17. Bill C says:

Well, we do know one thing: we became consciously aware at least once. I wonder if it can happen again.

18. Blunt Instrument says:

Boring.

Anyone who does not believe in life after death will applaud your reasoning.
Anyone who believes in a ‘supernatural’ soul will be unconvinced by anything you say.

This kind of argument merely confirms our internal biases and does nothing to foster meaningful discussion; assuming, of course that meaningful discussion between athiests and believers concerning the afterlife is possible.

In addition, your discourses concerning religion seem to presume that it would be preferable for people to not be ‘disillisioned’ about our place in the cosmos. I’m not convinced that a society consisting of athiests would be better.
Even without religion, bad people will find other justifications for their bad actions. But the good people who are struggling may find it considerably more difficult to pin all of their hopes on the vagaries of man.

19. AnotherSean says:

QFT is certainly not wrong, perhaps incomplete and maybe not fundamental. I’d say one of the lessons of QFT is that even mass is dynamical. This means to me that what ‘exists’ is not just a result of its history, but ultimately equivalent to it. If so, this does profoundly alter our notion of what it would mean to be immortal, because simple endurance through time would be seen as an approximation.

20. SteveB says:

Duh! The soul is made up of QFT ghosts…

21. Greg says:

I was left thinking that the author was a little too certain about his premise. After all, how did the universe begin? What was before the universe? Where did the fabric that this universe is composed of originate? I find Adam Frank’s ‘agnostic’ response to the soul a far wiser answer.

22. Arko Bose says:

I read a lot of comments and two things have become clear to me. Not everyone who read this post understood it. But that’s okay.

Here are two issues which I think need clarification (yes, even though Caroll has clarified them already!). First, we must concede that even if we assume that a “soul” exists and resides within the body, and outlives the body, then we must conclude that this “soul” interacts with the body. Now, the body itself is made of electrons, protons and neutrons, and gets continuously bombarded with neitrinos, and so on. The point is, that the physical interactions which the body is subject to at the energies at which the body remains as it is, are ALL well understood. The claim that there are many phenomena which occur within our bodies which are not understood at all is actually is misunderstanding of what is meant when we say “all physical interactions”. It means that all the “fundamental interactions” (i.e., all the interactions taking place among the fundamental constituents of matter) are well understood. Of course, what remains to be understood are the various complex reactions which the molecules take part in: ALL OF WHICH CONSISTENTLY OBEY ALL THE KNOWN PHYSICAL LAWS. This is the most important point: not a single observed phenomenon in the body violates or contradicts the known laws of physics. However, as Carroll explains, the very assumption that there may be a soul runs into a direct contradiction with these well-understood laws of physics.

Second, in response to the questions along the lines of: what if the soul is made up of an as yet unknown, unexplained form of matter (someone gave the analogy of dark matter and dark energy in argument, while admitting to not implying that the “soul” was actually made of these)? Well, let us assume that it IS actually made of some unknown form of matter. What then? Since it is made of some unknown form of matter, that form of matter will manifest itself through new interactions which it has with the known forms of matter (how, otherwise, can one even posit that a “soul” exists? Existence requires interaction.). However, ALL the interactions which known forms of matter exhibit are clearly and well understood, and this precludes the possibility that ANY new, unknown, unexplained, form of matter may interact with the known constituents of matter in a way which will be detectable in experiments which we can perform. And, if we can not detect any such interaction, how can we even talk about their existence?

This is the point which Carroll has tried to drive home, but was sadly missed by most readers.

23. Johnr says:

Well done, Dr. Carroll.

“I think therefore I exist….I think.” Once the plug is pulled (death), I will no longer think, and therefore will no longer exist in any form, other than a loose cluster of fragments of atoms. I agree with you.

Time to bury the witch doctor and move those wasted resources into science for the betterment of mankind.

Glad you survived the “end of the world” and hope for the same outcome in October.

24. jumbo says:

Arko Bose, if soul exist then it is expected to interact with our bodies via our will, emotions, conscience etc. Are you 100% sure that these can be derived from standard model? It seems to me that you start with assuming that reductionism is correct and not surprisingly you arrive to a conclusion that reductionism is correct.