endoself comments on Identity Isn't In Specific Atoms - Less Wrong

24 Post author: Eliezer_Yudkowsky 19 April 2008 04:55AM

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Comment author: PhilosophyFTW 29 May 2011 07:05:09AM -1 points [-]

Relying upon Wikipedia is not advised here. QM and GR, if you stick them together, entail everything. (On the assumption that from a contradiction one can derive anything. Paraconsistent logical systems deny this assumption.) For some proposition, sentence, statement or utterance that P, QM entails P. GR entails not-P. Absent abandoning classical logic (and moving to something like paraconsistent logic), GR and QM are inconsistent.

Let's assume that a theory is false if the theory entails P and not-P (that is, let's ignore paraconsistent logical sytstems). Then sticking GR and QM together entails P and not-P. Any theory that entails both P and not-P is false. So sticking them together fails.

Almost all physicists are happy with the above claims, and so there is an ongoing search for theories that preserve what's supposedly right about QM with what's supposedly right about GR. Enter theories of quantum gravity. These theories might be in some respects "quantum mechanical". That is, they preserve some aspects of QM. These theories aren't QM or GR, however. They're attempts to preserve what's right (let's suppose) about QM and make that compatible with what's right (let's suppose) about GR.

We're utterly in the dark about which such theories might be true. Sadly, that's the state of the game. If you appeal to QM in defense of some interesting claim, you are failing to appeal to a theory you ought, as an intelligent and well-educated person, place a high degree of credence in. Here our favorite blogger is is screwing up.

Comment author: [deleted] 29 May 2011 07:17:51AM * 0 points [-]

Relying upon Wikipedia is not advised here. QM and GR, if you stick them together, entail everything.

I'm confused how you got this out of the above -- I didn't mean to imply that QM+GR was consistent. They need fixing, and the article supports this viewpoint. Grandparent asked for citations; the relevant article has several. I didn't see the earlier comments between you and endoself, because they're not in this thread, but in another, for some reason. For what it's worth, I think you're misinterpreting statements intended for poetic effect.

So while endoself is wrong when he claims QM isn't inconsistent with GR, you're equally wrong for believing EY supports QM over GR, when in fact it's incredibly likely (based on everything we know about EY's stance on updating) that for now EY supports QM when it talks about small things and GR when it talks about big things, and that if some better theory would come along that explained the evidence better, EY would update to follow that.

Of course, I can't speak for him, but I claim the above is a more reasonable interpretation of the state of affairs.

EDIT: So there's a simpler litmus test to apply here -- has EY directly said anything about GR? If so, what evidence is leading you to believe he denies it?

Comment author: endoself 29 May 2011 08:50:30AM 0 points [-]

endoself is wrong when he claims QM isn't inconsistent with GR

I interpreted "QM is inconsistent with GR" as stating that GR cannot be quantized. This is usually what is mentioned in such discussions, as GR is much harder, maybe even impossible, to quantize as compared to other theories. There are very large advantages to only using the word 'consistent' in its precise mathematical definition, so I will do that from now on.

Comment author: PhilosophyFTW comment score below threshold [+] (3 children)

Comment author: PhilosophyFTW 05 June 2011 01:30:58AM -5 points [-]

In the simplest of terms, theory T is inconsistent with theory T* if the conjunction of T and T* entails everything in a classical logical system.

Since QM is inconsistent with GR, and since not every proposition is true, either QM or GR is, strictly speaking, false. Perhaps both are false.

The OP, Eliezer, must think that GR is false, since he's gone out and endorsed QM. This is not a good position to be in. More charitably, the OP has tried to endorse everything in QM that he thinks he needs for his argument, and he's asserted that all that requisite material will be retained in any future scientific theory.

The OP is then pleading that whatever physical theory turns out to be true will be sufficiently like QM that he's entitled to rely on QM in the ways he is. Call this quantum mechanical optimism or hopeful thinking. I don't see the argument here. Sorry.

He can conditionalize his claims. He can say things like, "If QM is true, then..." or "If the true physical theory preserves what there is in QM that I need for my argument, then..." But this isn't what he's doing.

And finally, even if the OP were to conditionalize, he'll still in hot water. Maybe the OP means by "physical nonsense" something like: contradicts claims that follow from QM. But he doesn't mean this. He's trotting in his own favorite little philosophical theory, without defense while pretending to rely upon good science (though he's in fact relying on very probably false science, since QM and GR can't both be true). This is evident when he writes: "The imaginary identity-tags that read "This is electron #234,567..." don't affect particle motions or anything else; they can be swapped without making a difference because they're epiphenomenal." Let's suppose that there are such particle-tags. Call them properties. And let's grant that they don't affect particle motion. Let's even grant that they're epiphenomenal. See how charitable I'm being to the OP?

Now obviously, it doesn't follow from QM that these epiphenomenal particle tags don't exist. The OP can beat his brain against the wall for the rest of his life and never manage to show it does so follow. Eliezer believes these particle tags don't exist, which is why he calls them imaginary, but he has not managed to produce one wit of evidence for that claim. I take it the OP would probably rely upon the following assumption: Nothing epiphenomenal exists. That's an interesting philosophical claim, and the OP can't pretend to defend it by giving us more very probably false physical theories. Nor does it follow from any physical theory the OP has mentioned so far.

When reading the OP, I am reminded of William Lane Craig's attempts to use The Big Bang to defend a central claim he needs for his Cosmological Argument: the universe had a beginning. Craig is in hot water here, for it does not follow from any of our best scientific theories, including all Big Bang Theories, that the universe had a beginning. Craig is using scientific dressing to peddle shoddy arguments that those unfamiliar with the science will be rhetorically overwhelmed by, and I don't see the difference between what he does and what the OP is doing.

Comment author: nshepperd 05 June 2011 05:20:36AM 0 points [-]

Well, yes. Two theories that make different predictions are logically inconsistent. The standard model of QM is wrong. General relativity is wrong. No-one here disagrees with this. However, the true theory of the laws of physics, when we obtain it, will have to explain all the experimental observations we have so far, which are predicted by the standard model to within 1 part in a billion in some cases. "The wheel of science ratchets forward, but never back" etc etc.

But you're right, in that all this quantum mechanics stuff is really beside the point anyway. You can apply the generalized anti-zombie principle in a newtonian or any other world just as easily (eg. as done in the first half of the article). Whether or not epiphenomenal particle-tags exist, they can't affect the physical cause of you saying "yes, I have continuing subjective identity", so they can't affect subjective identity. You don't have to assume that epiphenomenal particle-tags don't exist to conclude that they are irrelevant by, er, definition.

The only difference QM makes is that it doesn't talk about "particles" as fundamental entities, and hence "swapping two identical particles" is explicitly a no-op, which is nice, but not much more than an intuition pump.

Comment author: steven0461 05 June 2011 07:26:36PM 2 points [-]

Philosophers call these particle-tags "haecceities". The SEP has a good article on identity and individuality in quantum theory. From what I can tell, the parent comment is right except in that classical mechanics can be rephrased to not include particles as fundamental entities, and that quantum mechanics can be interpreted to include particles as fundamental entities (e.g. Bohm). Still, having particles be fundamental seems like a much clearer violation of Occam's razor in the quantum case than in the classical case.

Comment author: PhilosophyFTW 07 June 2011 02:50:44AM 0 points [-]

I didn't want to come out and talk about haecceitistic properties, since that would have made me sound even weirder (and it is controversial whether there are such), and I was already presenting some arguments in a hostile environment. But I had such properties in mind when responding. Thanks for providing the SEP link.

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