Friday, November 26, 2004

The Physics of Free Will

According to this article, mathematicians have proved a theorem linking particle physics to human decision-making:
It says that given three assumptions, if particles' behavior is truly predetermined, then people cannot have free will. In other words, if the behavior of a particle is fully determined by its past, so too are all the so-called decisions people believe they are making.

Conversely, if even one experimenter in the universe can make decisions that are not fully determined by the past, then every particle in the universe must be indeterminate as well, the theorem states.

Best make that four assumptions - it sounds like these researchers have never heard of compatibilism.

The most controversial aspect of the new theorem is likely to be the use of the term "free will" to describe a particular choice an experimenter can make. To many, the term belongs more to philosophy than to physics.

"If you bring up free will [in this context] in certain societies, people will say, 'Oh, you're a nut' straight away," Conway said. "Many will prefer a more mealymouthed term, like 'indeterminacy.'"

Well, there's a good reason for that. Namely, 'free will' and 'indeterminacy' are not the same thing. Treating them as if they were is an open invitation to conceptual confusion - as we see when the article starts talking about the "free will" of particles! (I take it they were being metaphorical, but still...)

Terminological quibbles aside, I'm not too sure what the big deal is here. (Perhaps a reader can explain it to me?) Isn't it generally accepted that if determinism is true of particles then it is also true of our brains? After all, the former constitute the latter. That could hardly amount to an "unexpected link" between physics and human decisions.

Rather, I take it that the interesting claim here is that the indeterminacy of a single decision requires the indeterminacy of "every particle in the universe". That's quite unexpected (to me, anyway). I would have thought that an indeterminate decision would merely require some indeterminate particles among those which constitute the person's brain. If this isn't so, then I guess that's of some (academic) interest.

But is it of any real significance to the free will debate? Has anybody ever suggested the indeterminacy of some particles but not others? Because that seems to be the only scenario that this theorem sheds any new light on. If I've understood it correctly, the theorem shows that partial particle indeterminacy is insufficient to produce indeterminate decisions. And that's the only new finding here (I take it everyone agrees about scenarios involving determinism or universal indeterminacy). So if nobody was suggesting partial indeterminacy to begin with, it all seems a bit irrelevant.

So, as I see it, framing the theorem as a breakthrough in the "free will" debate serves only to distract attention from its actual point of interest.

Have I missed something here? (It's entirely possible that I've misunderstood the article, in which case I'd very much appreciate any corrections!)


  1. I've never understood how randomness makes anything more free. Freedom is about conscious evaluation of different possibilities, plus deliberate action based on those evaluations. What, in any of this, is random at all? 

    Posted by Jason Kuznicki

  2. Jason - I entirely agree. I've always suspected that (lay)people turn to randomness because they confuse determinism with fatalism. But of course that is a mistake, as I discuss here.

    (But note that Robert Kane convincingly argues that some degree of randomness is at least consistent with freedom.) 

    Posted by Richard

  3. I don't think you've missed anything, and they definately have.

    For example, that free will (i.e. indeterminacy of future action) might be a property of a group, rather than an individual. i.e. a bunch of particles acting as a mind, where the group behaviour might influence each member in a way you wouldn't be able to predict from the properties of the member alone. Quantum Physics might lack the ability to describe the group behaviour.

    They've also mistakenly called their theorem "new", which might just be bad reporting. People have suggested this kind of thing before.

    Randomness doesn't make anything more free - indeterminacy does. Randomness is just the same as determinism, except that sometimes things happen for no reason. Indeterminacy (in a different sense to quantum indeterminacy) is about the nature of the arrow of time, and whether the future already exists. If the future already exists, it is harder to see how we have free will except in a compatibilist sense.

    What "proof"? Until physics can derive consciousness from particles, I don't see how they can make any claim about the nature of the will.

    Personally I suspect that the errors of thought are mostly on the part of the journalist rather than the mathematicians. 

    Posted by Tennessee Leeuwenburg

  4. The principle of indeterminatism is a principle that applies to everythign in the universe if htat is the thing they were relying upon to create free will then they are right it does extend to everything or nothing fopr a physisist the leap from explaining one example to explainig the whole universe in the same way is a natural one that barely needs explaining. I hardly think their analysis brings up anything new though.
    However I am with you on the compatabilism thing (i think) it is all a matter of what you hold constant which is realy an arbitrary philosophical decision not a fundimental aspect of the universe. 

    Posted by geniusNZ

  5. You've all missed the point. We are creations of evolution, hence everything we do must be programmed into us by natural selection. Therefore, the only sensible free will question is 'how come we think we're making our own choices when we're really just doing what we're told to do by natural selection?' To answer this we need to take a closer look at 'how we make a decision'. you can try this at home. As Matt Ridley says “I am quite capable of jumping in my car and driving to Edinburgh right now and for no other reason than that I want to.... I am a free agent, equipped with free will.” Matt Ridley, Genome

    But as Dr Ridley points out, we don’t just do things ‘for no reason’ - we do them because we ‘want to’… which is the big clue. Take a close look at how you make a decision and you'll see that everything you do is an attempt to make yourself 'feel good'.

    Which is the mechanism by which evolution controls our conscious choices: our conscious minds are programmed to attempt to maximise how good we feel. Hence the free will confusion is resolved - we're not really free, we've just been fooled into thinking that we are.


    Posted by The Conscious Robot

  6. Erm, conscious robot, I think you're missing the point of this post. I was simply talking about an unremarkable theorem that was being passed off as some great breakthrough. For my posts which actually tackle free will itself, see here.

    (Also, you're making the mistake of conflating 'free will' with the libertarian conception. But most philosophers are instead compatibilists, and there's nothing at all unscientific about that position.) 

    Posted by Richard

  7. It is a very important theorem. I would have preferred to see something based on aves, but they chose a particle type of explanation.

    Basically, determinism is finished. The universe cannot be deterministic, not the way Newton envisioned it. This is known to be impossible. Disorder does exist, but so does order.

    We now know that the negation of freewill is false. It remains to be proved whether freewill does in fact exist.

    Even Hawking's work on blackholes explicitly indicates that the universe cannot be completely deterministic, in fact paving the way for the very real possibility of freewill by disproving it's negation.

  8. I am a physics illiterate so please bear with me. From my limited understanding, there are two main theories of the universe and a everything in it. Firstly, there is the classical theory which states that all material conditions in the universe have prior material causes. Thus, if you had a God's eye view at the beginning of the universe you could predict the eventual position, velocity and trajectory of every single particle that will ever exist until the end of the universe. A bit like you could predict when and where every single domino in a domino rally will fall if you knew when and where the first domino was pushed over.

    The second theory is quantum. This seems to me to be essentially following the same rules of causality except that the first cause can be completely random. From then on upwards, though, it's classical all the way.

    To summarise, classical theory states that the universe is both determined and is, in principle, predictable. Quantum theory states that the universe is deterministic but is also, in principle, non-predictable.

    However, neither of the above two ways of conceptualising the universe and everything in it seems to allow for any kind of free will on the part of humans does it...

    Or am I missing something?

  9. Stephen - neither allows for the incoherent notion of ultimate responsibility, but either seems compatible with the more modest understanding of free will as merely a matter of exercising agency (acting on your own beliefs and desires).

  10. (Aside: your characterization of quantum physics doesn't sound right to me. It's supposed to involve ongoing indeterminacy. But, as noted in an earlier comment, indeterminism doesn't make us any more free.)


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