We’re flattered, but enough of the physics envy. It’s embarrassing us all.

A couple of days ago in the Guardian, Timothy Garton Ash highlighted how economics has been dangerously led astray by the baseless assumption that it’s a “hard” science like physics: When economists ignore the human factor, we all pay the price. It’s a convincing and compelling argument, and Garton Ash’s admonition of economists aspiring to the “status, certainty and predictability of physics” should be on the required reading list for all those who study and teach the dismal science.

This misplaced aspiration to reduce exceptionally complex, human issues to simplistic mathematical models, and to adopt the methodology and mindset of the physicist when it’s far from appropriate, is, however, widespread. Physics envy extends well beyond the confines of economics: the green-eyed monster is hardly a stranger in other social sciences. I’m not about to revisit the science wars  — nor am I about to loftily suggest that physics (and, more generally, the physical sciences) is purer-than-pure when it comes to peer review or its ability to sniff out a hoax — but Garton Ash’s article appeared just as I had finished reading a very recent, highly lauded, and exceptionally frustrating example of the misapplication of physics concepts in social science. It seems that, twenty years on from Sokal’s hoax, the social sciences still too often remain in thrall to their physical counterparts.

I can’t quite remember where I first read about Alexander Wendt‘s book, “Quantum Mind and Social Science: Unifying Physical and Social Ontology” but I suspect it was via Twitter (before I retired my account). It’s published by Cambridge University Press (so it’s got their imprimatur of adademic quality), and the reviews at their website are glowing: “a book of speculative grand theorising that is sadly lacking in the social sciences today”; “For most social scientists, all that Wendt takes us through will be a revelation. Wendt’s discussion of this material is just fabulous,”; “The author takes a courageous stance on a number of deep and difficult issues in philosophy of mind.”

Despite the title, I tried to give Wendt’s book the benefit of the doubt. I really did. And, to be fair, at times he does a fairly good job of outlining the history, the underpinnings, and the philosophical ramifications of quantum physics, including such challenging aspects as Bell’s inequalities, the EPR paradox, and entanglement. But there’s this right at the start of the book (p.3):

In this book I explore the possibility that this foundational assumption of social science [that we live in a world of classical physics] is a mistake, by re-reading social science “through the quantum”. More specifically, I argue that human beings and therefore social life exhibit quantum coherence — in effect that we are walking wave functions. I intend the argument not as as an analogy of metaphor, but as a realist claim about what people really are“. (Emphasis mine).


Just no.

This, the central theme of Wendt’s book (which runs to 293 pages excluding references), is demonstrably incorrect. We are not phase-coherent wavefunctions. Phase coherent interference of quantum mechanical pathways is the bedrock of quantum physics. As Feynman put it in the context of the double slit experiment: “We choose to examine a phenomenon which is impossible, absolutely impossible, to explain in any classical way, and which has in it the heart of quantum mechanics. In reality, it contains the only mystery.

If we were indeed walking wavefunctions then all of those quantum mechanical effects that we see at the single particle level would apply to our macroscopic world. And they clearly don’t. One of the very first concepts that physics undergrads (or, indeed, physics A-level students) encounter in their study of quantum mechanics is the de Broglie wavelength. There’s an exceptionally  simple relationship between the quantum mechanical wavelength of a particle/object (λ) and its momentum (p) which goes like this:

λ = h/p

where is Planck’s constant. (Apologies to the physicists who may be reading. You might want to skip forward a bit. There’s a ranty bit towards the end). For a typical human at typical walking speeds, that wavelength is not just negligibly small, it’s utterly beyond negligibly small. I’ll leave you to do the sums. (I’ll note in passing that “de Broglie wavelength” is not an entry in the index of Wendt’s book).

If we were walking wavefunctions of the type Wendt proposes then we would see the same type of interference effects in our everyday life that happen at the single particle level. We would diffract when we walk through doorways. We would be able to tunnel through walls without expending any energy. That blasted cat would indeed be simultaneously dead and alive.

(Edit 07/02/16:: I should clarify that even if humans were phase-coherent wavefunctions, and all other physics remained the same, the probability for tunnelling through a wall would still be unimaginably tiny. However, it’s clear from Wendt’s arguments that all other physics wouldn’t remain the same…)

But we don’t, and it isn’t. And the reason we don’t is exceptionally simple: we live in a world of classical physics. Wendt disputes this: “It has long been assumed that quantum effects wash out statistically, leaving the decohered world described by classical physics as an adequate approximation of macroscopic reality“.  But it’s not an assumption — it’s demonstrably the case that quantum effects “wash out statistically” as the system size/degrees of freedom/temperature increase. A vast amount of experimental data (coupled with an extremely well-developed mathematical framework) clearly shows this. No assumption necessary — there’s oodles of exceptionally strong evidence that demonstrates that human beings do not behave like quantum particles.

Moreover, we spend a great deal of time in undergraduate lectures teaching students to take the appropriate limit so that a quantum problem reduces to the classical situation (or a relativistic problem reduces to a classical scenario). One illuminating example is the case of Planck’s formula for the average energy per mode of blackbody radiation (to which Wendt refers on p.44 of his book) — this reduces to the classical formula (which is simply kT) in the appropriate limit(s). It is beyond misleading to suggest that it is only an “assumption” that quantum effects are washed out in the macroscopic world. There’s enough quantum woo out there from the likes of Deepak Chopra without accomplished academics such as Wendt (and prestigious academic publishers such as Cambridge University Press) adding to it.

Social science is important – it provides key insights into human behaviour and addresses questions that are beyond the scope of the physical sciences. I enjoy interacting and collaborating with my colleagues in social science both at Nottingham and elsewhere and gain a great deal from our discussions. But I’ll be brutally honest. I know for a fact that there are many in the “hard” sciences (and elsewhere) who would argue that the funding of social science is a waste of money and that it could be much better spent elsewhere. Misappropriating ideas from quantum mechanics in an attempt to ride on the coat-tails of the (highly successful) intellectual framework underpinning physics does social science no favours at all.

We physicists still don’t understand what the vast majority of the universe is made up of. So don’t envy us — pity us. And try to follow xkcd’s advice the next time you see “quantum” used outside a physics context…

Author: Philip Moriarty

Physicist. Metal fan. Father of three. Step-dad to be. Substantially worse half to my fiancée Lori, whose patience with my Spinal Tap obsession goes to far beyond 11...

13 thoughts on “We’re flattered, but enough of the physics envy. It’s embarrassing us all.”

  1. Yep there are far too many STEM professionals who wrongly ridicule social sciences and this book just gives them ammo.

    Thanks for that clear explanation. I actually followed it all and I learned something new in so the de Broglie wavelength was unknown to me.


    1. Thanks, Ravi. The problem is that the social sciences too often tend to get lumped together rather dismissively by those on the “hard sciences” end of the spectrum. Wendt’s book (and the pseudoscientific nonsense of others like Karen Barad) unfortunately adds fuel to the fire, as you say.

      There’s also the irritating tendency in some areas of social science for overly ornate and impenetrable writing (often disguising a lack of substance). Brigitte Nerlich wrote a great post on this a while back: http://blogs.nottingham.ac.uk/makingsciencepublic/2014/06/14/making-sense-in-science-and-in-public/

      This tends to obscure the value of many other areas of social science where the writing is sharp and engaging.


  2. Quantum has become the supernatural justification for all things. Instead of citing God – now people cite Quantum and think they are being more intellectual. But the reality is that they are just making a supernatural claim and then placing Quantum on it to make it sound real.

    Still, its disappointing that the Cambridge University Press…

    Liked by 1 person

    1. That’s exactly it. Deepak Chopra is one thing, but this is Cambridge University Press. Why do I suspect that the book was not sent to a physicist for review?

      Liked by 1 person

  3. Alexander Wendt is not a physicist, so maybe he can be excused for not understanding where quantum applies and where the classical world applies. It is odd that Cambridge University Press did not have a physicist vet the manuscript.

    There’s been a lot of research on the QM to classical transition. Unfortunately, this material does not appear to have made it into the undergraduate curriculum. For instance WH Zurek’s book and papers don’t seem to be widely taught in undergraduate programs, even though they can easily be understood by and undergraduate student.


    One artifact of quantum decoherence not being widely taught in undergraduate programs, is that people over apply QM to real world problems. It’s not just Wendt. I recently noticed that the Google Quantum Computing Group completely overstated the likely scalability of their recent work. They failed to address, in their widely publicized press announcement, that quantum decoherence would likely mean that their itty bitty quantum computer would not scale up, spatially.

    It’s my opinion that decoherence theory should be taught in undergraduate physics programs, if only to help students understand why, in their every day experience, they do not often experience the quantum world.

    Regarding the application of physics to economics, the social sciences, and even neurology: it is bizarre how frequently this occurs.

    Liked by 1 person

    1. Hi, Marnie.

      Thanks for those important comments. I agree entirely about the value of Zurek et al’s work on decoherence — there’s a link to Zurek’s book in the post. (And, yes, I’d love to know if CUP sent that book to a physicist for review!)

      “It’s my opinion that decoherence theory should be taught in undergraduate physics programs”

      I think that most undergraduate physics quantum courses at least mention the importance of decoherence but the focus remains on the “Shut up and calculate” style of delivery. As a lecturer myself I understand entirely why this is the case but we need to get back to discussing the knotty philosophical issues with QM.

      As Jane Randall put it, “There are a lot of mysteries about quantum mechanics, but they mostly arise in very detailed measurements in controlled settings.”



      1. I do think there is value in the classical mathematical physics developments of quantum mechanics, and also the mathematics of thermal and statistical physics. But I think this should be paired with experimentation. I found playing with various setups for Young’s double slit experiment and the Hall effect to stimulate my interest in how QM might relate to the real world. Even that is asking a lot in an undergraduate program. What I found strange once I got to the graduate level is that the physics discussions became very theoretical. There was very little discussion of real world phenomena. It’s in my engineering classes where there was an opportunity to discuss topics like quantum tunneling in a real world context. But still, there was very little discussion of decoherence theory.

        That being said, there are a number of real world examples that are best explained with quantum explanations. Here are some:

        Quantum tunneling (most electronic devices, including transistor and diodes, which exploit tunneling)

        Light emitting diodes


        Star color


        Thin film interference patterns (the color patterns you see on bubbles)

        Sunset green flash

        Blue sky (http://milesmathis.com/sky.html)

        Over the years, there have been various efforts to try to use QM to explain higher order neurological cognition in humans. My view: even if synaptic or neuron processing is subject to some quantum mechanical effects, human cognition is the product of many neurons firing together and in rapid succession. Therefore, again, decoherence would largely smear out any quantum mechanical effects.

        In terms of social phenomena like economics, there are multiple people involved, acting in an uncorrelated fashion, so there is another level of averaging (decoherence).

        This means that it is very, very unlikely for collective human behavior to exhibit any effects of the underlying quantum mechanical world.

        Maybe someone should let Cambridge University Press know.


  4. “In this book I explore the possibility that this foundational assumption of social science [that we live in a world of classical physics] is a mistake, by re-reading social science “through the quantum”. More specifically, I argue that human beings and therefore social life exhibit quantum coherence — in effect that we are walking wave functions. I intend the argument not as as an analogy of metaphor, but as a realist claim about what people really are“.

    Reminds me of Fritjof Capra.

    Liked by 1 person

  5. I am writing a philosophy PhD that criticises the extension of ‘scientific’ terminology in Wendt’s 1999 book, and I just discovered his 2015 one… I am almost speechless as to how he could honestly believe what he writes here. It’s very troubling to me that apparently articulate and intelligent people can produce books like this. What is the appropriate response? Sure we can criticise and point out the flaws, but will that really have an impact on how scholars like Wendt continue to think and write? Truly, we are living in the Feuilleton age as described by Hesse…


    1. Sorry for the delay in responding. I’m very interested indeed in your PhD. Would you mind sending me a copy of your thesis when it’s written? (philip.moriarty@nottingham.ac.uk)

      I think that all we can do is to continue to critique and debate. I find it remarkable that CUP published Wendt’s book but, on the other hand, if they had glowing referees’ reports I guess we can’t lay the blame entirely at their doorstep. There’s a large “emperor’s new clothes” element to much of this…


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