
Conway's Proof Of The Free Will Theorem - ramgorur
https://www.cs.auckland.ac.nz/~jas/one/freewill-theorem.html
======
eseehausen
As the final section shows, this is more about the question of determinism vs
indeterminism. Depending on your particular ontological and epistemological
leanings, that question and the question of free will may be the same, or
conflating the two may be a category error. I personally fall in the latter
camp, but this was an interesting foray into the musings of a brilliant mind.

~~~
tacotime
So you're saying the world can be deterministic and you can still have free
will? That would mean you would have to believe in something like souls then,
right? Something outside of this physical world that influences your physical
existence? I'm not questioning your views just trying to understand.

~~~
cokernel
There are varieties of compatibilism (the view that determinism and free will
are compatible) that do not require the existence of souls. I'd suggest taking
a look at Daniel Dennett's _Elbow Room_ for one example.

The Stanford Encyclopedia of Philosophy has an article on the subject:
[http://plato.stanford.edu/entries/compatibilism/](http://plato.stanford.edu/entries/compatibilism/)

~~~
DougH5000
Compatibilists redefine free will, similarly to those who redefine "god" as
"nature" or "the universe". Sure, anyone can define any term the way they
want, but it simply causes confusion to the majority of people who don't hold
such definition. Rather, it's best to abandon some terms as fiction, and
create new ones surrounding the concept you are looking to address. Better
books on the topic are Sam's _Free Will_ or Trick's _Breaking the Free Will
Illusion_.

[http://www.samharris.org/free-will](http://www.samharris.org/free-will)

[http://breakingthefreewillillusion.com/](http://breakingthefreewillillusion.com/)

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dgreensp
Conway's description of entanglement is misleading. FIN does not actually
apply here. According to quantum physics, no information is exchanged between
the particles. If information is exchanged, it is not limited to any finite
speed we know of.

The thought experiment he describes is well-known in the popular science
press: you create two particles with opposite spins (angular momenta), but
such that the spins are not determined. As soon as you measure the spin of one
the spin of the other becomes determined -- INSTANTLY. There is no speed-of-
light limit here. If you describe the situation as two particles colluding by
sharing some "information," then FIN does not apply, as far as we know! (And
if there is a limit, it is greater than the speed of light.) A physicist would
instead say that no actual information is transmitted, and entanglement cannot
be used to transmit information faster than the speed of light.

Since the metaphor of wave function collapse as information sharing between
particles leads to incorrect physics, I don't think we should read too much
into the metaphor of measurements as "free choices" of a particle.

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scythe
I'm surprised that people are so determined (heh) to pull determinism out of
quantum mechanics. I don't believe in metaphysical souls or free will per se,
but I also accept randomness in quantum mechanics (relational interpretation).

------
starmole
Interesting article. Thank you for posting.

I have a very limited understanding of physics but two questions spring to
mind:

1) Why is there little doubt in the axioms, especially FIN? It requires the
concepts of distance and time, either of which might not be applicable to the
resulting property.

2) Why call the resulting property "free will" or "free whim"? As far as I can
tell the proof is for the existence of an additional property to both the
experimenter and the particle, but there is no real description of it. This is
somewhat unsatisfactory addressed in the last paragraph, but really, why not
just call it a "randomness" or "god" instead of "whim"?

~~~
lmm
1\. Current physics - and in a way it goes back to Descartes and the very
first conception of modern physics, the idea that things happened for
mechanistic reasons rather than mysterious temperaments. If information can
travel instantaneously, doesn't that imply that distance and time are in some
sense meaningless? Also, relativity + faster-than-light information implies
causality violation, grandfather paradox and all of that. It's not "beyond all
reasonable doubt", but standard physics seems to respect it as an axiom.

2\. Because Conway likes attention.

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jlebar
If I understand this correctly, this proof is used to exclude one of the two
given explanations for the "Kochen-Specker Paradox"?

The article says the KS "paradox" implies that either

> 1\. Each measurement of a particle is not independent but rather depended on
> > context. In other words, the order in which you make measurements matters.

or

> 2\. The particle does not decide what the value of its spin is in any
> direction > until the experimenter actually makes a measurement!

As I understand it, the proof shows that the order in which you take the
measurements can't matter, excluding explanation (1), because of the following
thought experiment.

* Take two particles, entangled and then separated by some distance.

* More quickly than information can pass between the particles, measure one particle in three directions in some order, and measure the other particle just once in one direction which you choose right at that moment.

The second particle can't be affected by the order in which you measured the
first particle's spins, but if I was able to choose a direction in which to
measure the second particle's spin, then the second particle was able to
choose a result to match the appropriate result from the first particle's
measurements.

I think I followed this argument up until the last sentence above. What I
(mis)understand to be happening here is "spooky action at a distance"; it
doesn't at all appear to be a free choice on the particle's part.

In essence we established via the KS paradox that our two particles couldn't
have "agreed" on their spins ahead of time, because there's no consistent way
to assign all of their spins. But then we measured the two particles in the
proscribed way and got a result that looks like the particles did agree on
their spins beforehand.

I believe that this excludes explanation (1) from above, but I don't
understand how explanation (2) is consistent with this. If it were the case
that the particle was deciding its spin at measurement time (explanation (2)),
wouldn't the two particles have to communicate faster than c (or whatever our
speed limit is) in order to ensure that they made the same decision? We
explicitly ruled out this possibility via the FIN axiom and our experimental
setup.

The only way I can think of to make this work is to say that the universe
doesn't "choose" which result I got until I meet up with my friend who
measured the other particle. But this seems to be a far stronger claim than
the article makes.

What's the right way of thinking about this?

~~~
lmm
Talk about the particle "deciding" is coming from a Copenhagen interpretation
viewpoint. I find the many-worlds view clearer:

When the two particles are set up, their wavefunctions are in sync (or rather,
antisync) with each other. Particle A's wavefunction looks like an equal
superposition of up and down (at least, when projected onto a single axis; the
wavefunction for the full particle incorporating all the possible axes is more
complicated); Particle B's wavefunction is the same but 180 degrees out of
phase, so that A is up whenever B is down and vice versa.

When you make a measurement of particle A, you entangle yourself with it; that
is, your own wavefunction becomes in phase with its. (Again, it's still an
equal superposition between having measured up and having measured down). When
your friend makes their measurement of particle B, they entangle themselves
with it in the same way. So when you meet up with your friend, your
wavefunctions are in (anti)phase; the universe as a whole is an equal
superposition of the world where you measured up and your friend measured
down, and the world where you measured down and your friend measured up.

(What does being in that superposition look like, subjectively? It looks like
a 50% probability of the first world and a 50% probability of the second
world. Which agrees with what we measure when performing the experiment)

~~~
jlebar
Thanks for the reply!

> When your friend makes their measurement of particle B, they entangle >
> themselves with it in the same way. So when you meet up with your friend, >
> your wavefunctions are in (anti)phase; the universe as a whole is an equal >
> superposition of the world where you measured up and your friend measured >
> down, and the world where you measured down and your friend measured up.

If we take this perspective, are we still able to rule out possibility (1)?
That is, our assumption was that what my friend did couldn't affect my
experiment; we used this fact to rule out the possibility that the order of my
friend's measurements affected my result. But if in some sense my experiment
doesn't "occur" until I meet up with my friend, then this assumption seems not
to be true any longer. Which is to say, we could explain this whole thing
without requiring any "free will" / "true randomness" on the part of our
particles.

~~~
lmm
From a many-worlds point of view there's not the same nondeterminism in the
physics. There's nondeterminism in our subjective experience, but it's a
surface phenomenon rather than something fundamental.

So I guess we've sidestepped the question the "theorem" is aimed at, because
by adopting this viewpoint we're already assuming that humans don't have any
kind of physical nondeterminism (or "free will", if you insist).

Personally I think the idea was stupid as stated; having a set of dice inside
your head doesn't make you any more likely to have "free will" than if you
didn't, and that's all that quantum nondeterminism really means. But I guess
some philosophers really did claim that this was support for the notion of
free will, so it's worth refuting that as directly as possible.

So I guess you're right: if anything, a many-worlds interpretation gives more
support to the idea that quantum nondeterminism has something to do with free
will, because it means the nondeterminism only comes in when we look at a
human's subjective observations. So yes, I think we really do sidestep the
claim this way.

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tacotime
I don't know about all that quantum math craziness or that spin fin twin
nonsense but it sounds like Conway shares a long standing sentiment I've had
that "free will" is a story we tell ourselves because we want to believe our
choices are based on something fundamentally more complex or important than
the choices of an animal or a computer. Even if "free will" is a real thing
and not just an illusion, what is it really but random in-deterministic
variations, or what Conway called whims.

I remember when I voiced these opinions in my college philosophy class to a
room full of denialists. It's good to know I'm not alone in my thinking in a
world where multi-verse and string theory are sooner accepted than the fact
that free will is an illusion.

~~~
JackFr
Your response is ripe with irony.

'A world where multi-verse and string theory are _sooner accepted_ ...'
indicates a world where there is agency, and thus will. We won't even go near
your normative subjective ideas about the 'good'.

You can't both deny the existence of free will, and castigate those whom with
you disagree. If you're right, then none of us can be wrong -- certainly no
more than a plant or a rock or the moon can be wrong.

~~~
sjy
It is easy to imagine a computer program that is both deterministic and wrong.
Why not a person?

~~~
JackFr
When one describes a computer program as "wrong" it is within the context of
what some other agent wants or expects it to do. As a purely physical process,
it can never be wrong or right, it can just be.

~~~
Houshalter
You have defined "wrong" in an incredibly strange and useless way. 2+2=5 is
"wrong" regardless what agent you are or what universe you exist in.

------
danielrm26
I'm not sure where to start.

The first diagram of the proof starts with "there exists some experimenter
with at least some free will". That's a problem, as it uses the argument's
conclusion as one of its premises.

Using a simpler example, it'd be like saying, "To prove that aliens exist, let
me show you three simple steps: 1) let's assume aliens exist, 2) ...

The second problem here is that he seems to be trying to illustrate that if
things cannot be predicted that we have free will. This is a common fallacy in
the free will debate. Randomness is an attack on fatalism, but offers ZERO
degree of control to humans, and therefore has no place in the free will
debate.

Finally, if you want to see a much better argument, in the other direction,
check out my Two Lever Argument Against Free Will that uses 25 lines of Ruby.

[http://danielmiessler.com/blog/two-lever-free-will-
ruby/](http://danielmiessler.com/blog/two-lever-free-will-ruby/)

~~~
pjungwir
> it uses the argument's conclusion as one of its premises.

His theorem doesn't assert free will. It asserts that if experimenters have
free will, then particles have free will. So if it's wrong, then it's not for
the reason you give.

~~~
danielrm26
I think he's asserting that if experimenters have free will, then particles
do, which means we do as well.

This isn't a proof of particles having free will. That's an intermediary step
to saying we have it as well, and therefore you can start with a step that
says we do.

~~~
jamesaguilar
You need to read it again. The person you're replying to has correctly stated
what is shown.

