philosophy vs. physics

[pau17]

http://lesswrong.com/lw/ph/can_you_prove_two_particles_are_identical/

Is physics taking over philosophy’s territory? Is this beat-down on philosophers fair? If philosophy still has a necessary place within physics, what is it?

"I'm sorry, this isn't a question of physics, it's a question of epistemology. To believe that all aspects of two particles are perfectly identical, requires a different sort of assurance than any experimental test can provide. Experimental tests only fail to establish a difference; they do not prove identity. What particular physics experiments you can do, is a physics question, and I don't claim to know that. But what experiments can justify believing is an epistemological question, and I am a professional philosopher; I expect to understand that question better than any physicist who hasn't studied formal epistemology."

And of course, Bob is wrong.

Bob isn't being stupid. He'd be right in any classical universe. But we don't live in a classical universe.

And the flaw in Bob's logic? It was a fundamental assumption that Bob couldn't even see, because he had no alternative concept for contrast. Bob talked about particles P1 and P2 as if they were individually real and independently real. This turns out to assume that which is to be proven. In our universe, the individually and fundamentally real entities are configurations of multiple particles, and the amplitude flows between them. Bob failed to imagine the sequence of experimental results which established to physicists that this was, in fact, how reality worked.

You can read the full post and further debate in the commentary section; the excerpts quoted here are the crux of the matter but it gets a bit more in detail. A few interesting points from the comments:

IL: But the experiment doesn't prove that the two photons are really identical, it just proves that the photons are identical as far as the configurations are concerned. The photons could still have tiny tags with a number on them, but for some reason the configurations don't care about tags.

Yes, that's the part where the observed universe is a lie.
I have difficulty expressing in words exactly how fundamental is the notion of configurations. Now that we know about them, our old ideas about particles have gone away, or rather, been made strictly emergent in configurations... what you just said is the same probability as discovering that apples aren't made of atoms after all, but are in fact fundamental apples.
The configurations are reality, the underlying fundamental from which the appearance of individual particles emerges; they are not something tacked on.

I don't think that the problem is that it is impossible with effort and training to learn to recognize one's blind spots a-priori. Rather, I think that philosophy attracts many kinds of people, only one of which is the type of person who has a talent that he wants to develop in recognizing his blind spots. Philosophy then provides, to different extents in different places and times, some training in this skill and some reward of status for the development of it. Currently, it seems to me that neither Analytic nor Continental philosophy provides significant training or status relating to this as opposed to other skills. More particularly, both seem to provide far less such training or reward in status than contemporary theoretical physics, theoretical computer science and probably some parts of math.
The main problem, it seems to me, relates to this issue of rewarding with status. In physics, ultimately status goes to those who make the correct predictions enabling correct beliefs to actually attain dominance in the field even if they are counter-intuitive (or too intuitive to qualify as 'deep'), while in philosophy, without experiments, correct beliefs always exist at a very low incidence at equilibrium, far less popular or 'official' than clever descriptions of those cognitive illusions such as empty labels http://lesswrong.com/lw/ns/empty_labels/ (in this case, the particle without the mathematical relationships it participates in) that act as attractors to human naive ontology. As a result, the average physicist is better at this type of philosophy than the average philosopher is, while the average highly esteemed physicist is astronomically better at it than the average highly esteemed philosopher.

 

[uppi]

Philosophy is all fine and needed to argue about and interpret things where there is no or where there cannot be experimental evidence. However, where there is experimental evidence which contradicts an philosophical argument, then that argument is wrong, no matter how dear it is to philosophers.

That might be seen as physics taking over philosophy's territory and I'd argue that this is the point of physics: To settle as many philosophical questions as possible, so that philosophy has solid basis to try to answer the remaining ones.

If you do philosophy and ignore the experimental evidence, your ideas are likely to end up being wrong. If you argue in favour of a deterministic universe, you should have a very good explanation for all the experiments showing indeterminism. Otherwise you're just being wrong instead of doing philosophy.

 

[SS-18 ICBM]

Philosophy doesn't use numbers and statistics.

 

[lovett]

"Bob's" most important comment is:

"What experiments can justify believing is an epistemological question."

This is true. I don't see how it could be otherwise. The rebuttal intends to refute this by telling Bob what kind of universe he lives in. This is based on experimental evidence. It's a circular argument.

Not to say that Bob's position on particle identity is correct. As he admits he may not understand the experiments in question. It does show that experiments can't be self-justifying; what they can justify is an epistemological question. Epistemology completely underpins science. Without it science is an empty vessel.

 

[Mise]

But the author is acknowledging the epistemic limits of experimentation, by acknowledging the problem of induction, for example. The author says (paraphrasing from memory) that to the extent to which we can say that the sun will rise tomorrow, we can say that particles are indistinguishable. We don't live in a universe in which the sun won't rise tomorrow; neither do we live in a universe in which particles are fundamentally distinguishable.

EDIT: Found the relevant section:

But for the Sun to transform to chocolate cake requires more than an unanticipated discovery in physics. It requires the observed universe to be a lie. Can any experiment give us an equally strong level of assurance that two particles are identical?

Answer: Yes, it can, and it has.

 

[Atticus]

I thought not to post to this thread, since this is one of those subjects where people often misunderstand me, but here we go anyhow....

The author does poor work explaining the problem of induction. He portrays it as juvenile philosophical nitpicking, like only way to deny the legitimacy of induction was to resort to juvenile idiocy ("how do you know that sun doesn't transform into a chocolate cake?").

However the problem of induction is very real, as you haven't necessarily always taken into account everything that matters. Imagine Galileo performing tests on the acceleration of falling body. He is so obsessed with the thing that he builds vacuum and very precise clocks, and eventually concludes that the acceleration is 9.807 +/- 0.005 m/s². Then pope exiles him into Calcutta, and as he continues experiments there, it turns out he was wrong.

Ok, some of you might object that he wasn't, that he was right about the acceleration in Pisa. But his original conclusion didn't say anything about locations. Inductive reasoning gone wrong can perhaps be often corrected by adding some conditions, but that doesn't mean that it wasn't wrong before that.

It's impossible to take into account every possible condition for experiment. Otherwise we'd have to add clause "when someone is observing" to every result, for example.

There's also examples of theories that were thought to be correct that turned out to be false. Why would current theories be any different?

Also all the speech about the probability of theory failing is nonsense. No probability can be assigned to such theory (unless it's 0). The only meaningful way to speak about probabilities would be to say that probability of A is greater or equal to that of B in cases when B => A. In other cases the author can at best say "it seems very unlikely".

Now Galileo in our imagined example might have said that it's very unlikely that the acceleration of falling body is something else than his experiments showed. He says, it's something like 0.0000001%. Once he's in Calcutta, it's 100%.

Of course there are some things that it would be very absurd to deny, like that the sun rises tomorrow. You can mistake about acceleration of gravity, but not on this fact. It can be wrong only in theory, and you'd rather doubt your sanity than believe any falsifying observation.

Spoiler however: :

Besides the theory doesn't have to be incorrect for two particles to be nonidentical, incomplete suffices for that.

The problem is that some people have to have certainty. Why couldn't we just live with the possibility of error rather than claiming that things which look like very likely are true?



Disclaimer: I won't participate very long in any discussion that misunderstands my points here fundamentally. I'm not physician, but apparently it didn't stop the author of the article in OP to participate, contrary to his advice to other people. Furthermore, I've heard that science is reliable because it's open to critique.

 

[uppi]

You make good points and, yes, the limits of a theory and the limits of current experimental evidence always has to be considered.

However, the indistinguishability of particles is so fundamental to modern physics that it would be comparable, if you allow me to continue your analogy, to Galileo claiming, that things do not fall down at all.

A new theory that makes an old theory obsolete becaues the limits of the old one have been exceeded has to reproduce the effects the old theory explained. Although Newton was wrong about how gravity worked, all the effects that have been predicted by his theory and then validated by experiment have to be a part of any new theory of gravity. Similarly any new theory obsoleting current quantum mechanics must account for the difference of distinguishable and indistuingishable particles. Thus, even if it may have to be extended, the concept has to stay.

 

[Atticus]

This post isn't directed at your post above, Uppi. I'm not contesting indistinguishability of particles here, but I think Eliezer (the writer of the article quoted in OP) has understood the whole thing wrong.

To say "it would be absurd to think this would turn out false" is in itself epistemology.

It has been well and long known that many things we take for granted are impossible to prove (as with mathematical rigour). However there are things we are absolutely sure that they are true, and we can't entertain possibility of being wrong. And there are few times when we find out that we indeed have been wrong.

We don't have to go into physics to find things we can not prove, but are absolutely certain about. I'm for example pretty sure that you other posters in this thread are actual human beings, that my mother isn't Satan, that none of you have swallowed supernovas, or that the Sun isn't a chocolate cake.

Epistemology deals with this gap: What should we call knowledge? Requirement of proof would be too much in real life, and absurd in itself. However there has to be some criteria.

So the end of epistemology is not really the high school kid saying: "you can't prove that, how do you know that everything isn't dream, lol!", unlike Eliezer seems to think. It's more like the begining of it.

So Eliezer portrays philosopher falsely. Notice also that the title of the article says: "Can You Prove Two Particles Are Identical?", but in the article he asks the imagined philosopher, if he knows whether they are identical. The mix in use of these words is actually quite subtle, and goes easily unnoticed, but the difference it makes is huge. Adequately read philosopher would ask Eliezer what he means by "know", because the general consensus among philosophers is that knowledge does not require proof.

So perhaps Eliezer should heed his own advice (paraphrased): "You Are Not A Philosopher. Maybe you shouldn't be so glib when it comes to saying what philosophers can or can't know."


(Yeah, it isn't very nicely said, but Eliezer's smug style annoys me, and he's not here reading this, so the temptation is too much to resist. This isn't my own attitude to people who haven't read or thought things).


Eliezer seems to see philosophers and epistemology as enemies of physicists, and I guess it's not that uncommon attitude. Besides philosophers can be really annoying. He seems to think that philosopher's aim is to show that physicists are wrong, but I don't think that's the case. Competent physicists do know what they are doing, and common sense is enough for them. They don't need any more sophisticated theory of truth than "it would be absurd to think otherwise", nobody does really. Philosophers are trying to explicate this theory, or to make it systematic.

More adequate case in physics vs philosophy would be for example philosophy of time or matter, where physics has produced some special knowledge, but philosophers aren't always studious enough to find about it (I mean non-hc philosophers, students and such. I presume most publishing philosophers do read about these things).

Most reactions this article comes from the words "prove" and "know". If Eliezer had used consistently only "prove" or only "know", I don't think this would cause very much turmoil: The physicists would say "so what? We can't prove it, this is physics, not maths!", or the philosopher would say "I'd never claim that he doesn't know it".

And I'm sorry, because you all deserve better articulated post than this, but unfortunately I'm not able to write one. If someone in this thread thinks that this is attack against him, he has misunderstood the post.

 

[Mise]

I see what you mean about the interchanging of "prove" and "know" now, on second reading.

 

[uppi]

More adequate case in physics vs philosophy would be for example philosophy of time or matter, where physics has produced some special knowledge, but philosophers aren't always studious enough to find about it (I mean non-hc philosophers, students and such. I presume most publishing philosophers do read about these things).

The problem is, that reading about it is not sufficient, they also have to understand it. We cannot exactly blame them, if they get it wrong, as getting it right is quite hard, but it still annoys physicists if someone badly misinterprets physics yet again.

(It isn't as as bad as with the media, though. Once you notice what kind of crap they write on your field, you have to wonder how accurate they are when they write about other fields, where you don't know enough to spot all the errors.)