Consistent Histories solipsism?

[JamieSalaor]

Sounds like Last Thursdayism when you put it like that.
So, if one is to take CH literally it might be reasonable to argue that you can't definitely conclude that the past happened.
Thing is, though this is potentially a logical conclusion of CH the fact its so astronomically unlikely and so unfalsifiable seems to take credence from the CH interpretation in my opinion..

I don't think it would ever really be reasonable to deny the existence of dinosaurs etc...
Plus wouldn't this contradict relativity. If I am stood 66 million years away, surely that light would contain evidence proving dinosaurs...?

 

[PeterDonis]

though this is potentially a logical conclusion of CH the fact its so astronomically unlikely and so unfalsifiable seems to take credence from the CH interpretation in my opinion..

Please bear in mind that the position you are criticizing (and I'm not saying your criticism isn't reasonable) is not "the CH interpretation"; it's Dowker and Kent's particular version of the CH interpretation. I don't think all advocates of the CH interpretation in general would agree with their particular version of it.

If I am stood 66 million years away, surely that light would contain evidence proving dinosaurs...?

You can't instantly transport yourself from here to 66 million light-years away. If you were there now, you would have had to leave Earth earlier than 66 million years ago (since you can't travel as fast as light does). Yes, if you had done that you would, 66 million light-years away "now", be seeing light from Earth that would (with a sufficiently powerful telescope) show images of dinosaurs. But those images are still not the same as the dinosaurs themselves, or the events on Earth that emitted the images. There is still an astronomically unlikely possibility that some quantum fluctuation could have produced the images, without the events on Earth that they appear to be images of ever having actually happened.

In other words, no, you can't rule out Dowker & Kent's version of the CH interpretation on these grounds.

 

[JamieSalaor]

I think that's fair yeah.
I haven't seen any other papers on CH that seem to imply solipsism... At least as heavily as they do.

Am I right in saying that the point of the paper was to pick out the flaws in CH.
As interpretations that lead to such conclusions are often heavily criticised...

I understand you're not really a supporter of CH but what do you think of Dowkers interpretation of CH..
Do you think it's unfair, or perhaps rooted in a contrasting understanding to most CH supporters?

I assume most if not all scientists deny solipsism of the moment. It's very much a useless proposition.

 

[PeterDonis]

Am I right in saying that the point of the paper was to pick out the flaws in CH.

You would have to ask the authors what the intended point of their paper was.

I understand you're not really a supporter of CH

Where did I say that?

what do you think of Dowkers interpretation of CH

I think that, as you said, it's not a very reasonable interpretation, although, as I said, it can't be ruled out on logical grounds. If the only consistent histories that contain our present experiences of things like dinosaur fossils but don't contain actual dinosaurs in the past are the astronomically unlikely "quantum fluctuation" ones, then I think it's perfectly reasonable to say that dinosaurs existed in our past.

I assume most if not all scientists deny solipsism of the moment.

I don't think most scientists would even have such a hypothesis on their radar to begin with.

 

[JamieSalaor]

Dowker and Kent in their paper explicitly mention that they do not think solipsism is respectable. There I believe that the purpose of the paper must have been to locate flaws as they don't seem particularly find of their interpretation..

I thought I saw you say you didn't really ascribe to any interpretation on a different thread but I may be mistaken...

I very much agree dowker and Kent are not proposing a reasonable interpretation but I feel as if they knew that.

Yeah I very much agree it seems very unreasonable to deny the existence of the dinosaurs. At that point you can just start denying what you want...
Then again though if I ever cheat on someone I can simply point them towards Dowker and Kent's paper...

By the way PeterDonis you've been really helpful on a few threads I've been a part of so thank you!

 

[PeterDonis]

I thought I saw you say you didn't really ascribe to any interpretation on a different thread

I have said that in other threads, yes. But I have also said that I am quite willing to make use of various interpretations when it seems useful to do so. So the fact that I don't "believe in" any particular interpretation does not mean I don't "support" interpretations, in the sense of not thinking they're useful for anything.

PeterDonis you've been really helpful on a few threads I've been a part of so thank you!

You're welcome!

 

[JamieSalaor]

Do you support the CH interpretation put forward by Dowker?
If not, which formulation of CH do you support, if any?

 

[PeterDonis]

Do you support the CH interpretation put forward by Dowker?

I don't think it's a reasonable interpretation, but, as I've said, it's not ruled out on logical grounds.

which formulation of CH do you support, if any?

If I were making use of CH to analyze a particular scenario, I would be looking at reasonable histories--the ones that don't contain astronomically unlikely events that create present records of things that didn't actually take place in the past.

 

[JamieSalaor]

@Morbert I'd love to hear what you think about all this.
Would you agree it's not possible to rule out on logical grounds?

Thanks!

 

[Morbert]

@Morbert I'd love to hear what you think about all this.
Would you agree it's not possible to rule out on logical grounds?

Thanks!

Not possible to rule out what on logical grounds?

 

[JamieSalaor]

In reference to Dowker and Kent's interpretation of Consistent Histories.
The idea that due to the 'rules' of the interpretation its not possible to entirely conclude that dinosaurs existed and that the fossils are instead not astronomically unlikely quantum fluctuations (as discussed previously between me and Peter)

Also would you say that your preferred interpretation of CH would conclusively say that past life can be deduced by the existence of fossils. Not that they are instead fluctuations...

Thank you!

 

[Morbert]

In reference to Dowker and Kent's interpretation of Consistent Histories.
The idea that due to the 'rules' of the interpretation its not possible to entirely conclude that dinosaurs existed and that the fossils are instead not astronomically unlikely quantum fluctuations (as discussed previously between me and Peter)

Also would you say that your preferred interpretation of CH would conclusively say that past life can be deduced by the existence of fossils. Not that they are instead fluctuations...

Thank you!

I do not think Dowker and Kent's critcism stand up to scrutiny, for reasons I mentioned previously. And I think dinosaurs constitute an inference to the best explanation for the fossil record.

 

[Halc]

If the only consistent histories that contain our present experiences of things like dinosaur fossils but don't contain actual dinosaurs in the past are the astronomically unlikely "quantum fluctuation" ones, then I think it's perfectly reasonable to say that dinosaurs existed in our past.

Far more likely than this 'improbability drive' scenario (from Hitchhiker's guide) you describe is a sort of Boltzmann brain scenario where a small system somewhere (much smaller than a planet) is by chance put into a state best explained by a history of dinosaurs and such despite the nonexistence of them in actual history. I don't know if that counts as a valid state in CH since I'm restricting the system to a small system and not the entire universe in one 'present' state, which is itself by definition a counterfactual. The small system still qualifies as an astronomically unlikely "quantum fluctuation", but perhaps less so than one that by chance puts actual fossils of never-existent things in consistent locations around the planet. This small system would imminently be put into an inconsistent state when its surroundings do not match the history that best explains its current state, but solipsism of the moment cares not about future states of the system.

I carefully use the word 'system' and not 'observer' or 'knowledge' since none of the primary (holding to methodological naturalism) QM interpretations assign any special significance to a biological thing.

 

[Morbert]

Far more likely than this 'improbability drive' scenario (from Hitchhiker's guide) you describe is a sort of Boltzmann brain scenario where a small system somewhere (much smaller than a planet) is by chance put into a state best explained by a history of dinosaurs and such despite the nonexistence of them in actual history.

Just to clarify the notion of a history containing or not containing dinosaurs, since there are two notions of "not containing dinosaurs".

Consider a measurement scenario similar to one I described earlier, but a bit simpler: We have a particle $s$ prepared in state $|Z^+\rangle\langle Z^+|$, and device $M$ that measures the spin-$X$ of $s$. Like before, we consider two times: one before measurement and one after. So we have a history space $\mathcal{H}_{t_1}\odot\mathcal{H}_{t_2}$ and, at each time, a state space that is a product of the particle and device state space $\mathcal{H}_{t_i} = \mathcal{S}_{t_i}\otimes\mathcal{M}_{t_i}$. Now consider two incompatible sets of consistent histories $\mathcal{F}_1$ and $\mathcal{F}_2$.

$\mathcal{F}_1$
\begin{eqnarray*}
[X^+]\odot [M^+]\\
[X^-]\odot [M^+]\\
[X^+]\odot [M^-]\\
[X^-]\odot [M^-]
\end{eqnarray*}$\mathcal{F}_2$
\begin{eqnarray*}
[Z^+]&\odot& [M^+]\\
[Z^+]&\odot& [M^-]\\
[Z^-]&\odot& I_{\mathcal{H}_{t_2}}
\end{eqnarray*}
Now let's say the device produces a datum $M^+$. Notice the set $\mathcal{F}_1$ contains the history $[X^-]\odot [M^+]$, which will have a probability that is small but not exactly 0. Equivalently We can compute the conditional probability $P(X^-|M^+) \approx0$. This implies the chance that the particle has spin $X^-$ at time $t_1$ and the device produces the seemingly contrary datum $M^+$ is small but not exactly zero, meaning there is a very very very slight chance that the datum produced by the device does not match the property it is supposed to record. This is analogous to the improbable history that asserts dinosaurs never existed even though there's a fossil record that heavily implies they did. So, using this analogous set, we can conclude that it is very highly probable that dinosaurs existed if we observe fossils of them.

Now consider $\mathcal{F}_2$. This set contains assertions about spin-$Z$ of the particle at $t_1$, so we can't interpret an outcome like $M^+$ as a measurement of spin-$X$ using this set, because properties like $X^+$ and $X^-$ are indiscussible in this set. It is sets like these that Dowker and Kent use to argue CH implies solipsism. Note that, in this set, no history contains spin $X^+$, and at least one of them has to be the history that occurred. So by selecting $\mathcal{F}_2$, we have guaranteed that $X^+$ doesn't exist. Similarly, we could select a set that doesn't contain statements about dinosaurs in any history, and therefore erase them from existence. Where have we gone wrong?

The subtlety is that histories like $[Z^+]\odot [M^+]$ are *not* analogous to dinosaurs not existing in spite of records. In histories like these, dinosaurs are indiscussible. The set $\mathcal{F}_2$ does not guarantee that dinosaurs don't exist. Instead it is a set that is not suitable for discussing the existence of dinosaurs.

 

[JamieSalaor]

Would this be comparable to us discussing the making of a crochet sweater. It's a discussion about crochet hooks and wool.
Not at all useful for discussing the existence of dinosaurs, but it doesn't deny their existence. But instead says nothing about them?

 

[JamieSalaor]

Also, I'd really like to hear more about why Dowker and Kent originally concluded in not just solipsism of the moment but pure solipsism.
I'm starting to thick their accusations are relatively silly, based on all you've told me.

 

[Morbert]

I don't think they conclude pure solipsism. E.g. in the paper they say this solipsism can be avoided when CH is applied to quasiclassical domains.

 

[JamieSalaor]

Do you think that CH implies solipsism when applied to other domains?

 

[Morbert]

Do you think that CH implies solipsism when applied to other domains?

I don't understand the question.

 

[JamieSalaor]

You say solipsism is avoided in quasi classical domains.
Is that the macroscopic?

 

[Morbert]

You say solipsism is avoided in quasi classical domains.
Is that the macroscopic?

Quasiclassical domains are consistent sets describing hydrodynamic variables. The regular phenomena we experience belong to a quasiclassical domain, but quasiclassical does not mean macroscopic. There are macroscopic properties that are not quasiclassical.

 

[JamieSalaor]

So, would that mean that as there are non quasiclassicaly macroscopic properties then solipsism in CH is still implied?
Or would you still say Dowker and Kent are mistaken?

Basically, do you disagree with their charges of true solipsism?

 

[Morbert]

So, would that mean that as there are non quasiclassicaly macroscopic properties then solipsism in CH is still implied?
Or would you still say Dowker and Kent are mistaken?

Basically, do you disagree with their charges of true solipsism?

Unless I am missing something, Dowker and Kent don't charge CH itself with true solipsism. Could you highlight where they do?

 

[JamieSalaor]

They ultimately go on to argue that CH implies solipsism an I will get to that but I have so far only addressed their first charge, which is that since CH does not sharply define the notion of an "actual history" it accommodates all sorts of notions of an actual history, including solipsism of the moment. They see this as a negative point.

You note that they go on to imply solipsism.
Did you simply mean solipsism of the moment?

 

[Morbert]

You note that they go on to imply solipsism.
Did you simply mean solipsism of the moment?

They go on to argue that CH implies solipsism of the moment for reasons I addressed earlier, and solipsism if an "IGUS-centric" version of CH interpretation is adopted, but then remark that solipsism can be avoided if CH is interpreted in terms of quasiclassical domains. I don't believe it is necessary to appeal to quasiclassical domains to see off solipsism but they at least accept that CH does not necessarily imply solipsism.

 

[JamieSalaor]

Would you says an IGUS centric interpretation would be unreasonable?
Also, do you agree that if that position were taken CH would be solipsistic?
As they say in the paper that don't think solipsism is reasonable so I assume they do not think an IGUS centric will be... Thanks so much for all your input!

 

[Morbert]

Would you says an IGUS centric interpretation would be unreasonable?
Also, do you agree that if that position were taken CH would be solipsistic?
As they say in the paper that don't think solipsism is reasonable so I assume they do not think an IGUS centric will be...Thanks so much for all your input!

I think the IGUS-centric interpretation is a misunderstanding of CH, for the same reasons I mentioned previously (omission of a property from a set is not a declaration of non-existence). We can construct the IGUS sets Dowker and Kent talk about without committing ourselves to solipsism.

 

[JamieSalaor]

Seems then at the end of all this since even IGUS centric interpretations aren't committed to solipsism. There is absolutely no reason to say CH is solipsistic. Also, dowker and Kent made some unreasonable assessments of the CH interpretation, by attributing things like solipsism to it.

Would you agree with this?

I'm happy to conclude now if so you've basically cleared so much up
Thank you so much for everything!

 

[JamieSalaor]

Also would you say most consistent historians agree that CH does definitely not imply solipsism?

Thanks!

 

[AlexCaledin]

The most consistent historian is Robert Griffiths! He says in the very end of his book,
page 370,

To be sure, neither quantum nor classical mechanics provides watertight arguments in favor of an independent reality. In the final analysis, believing that there is a real world "out there", independent of ourselves, is a matter of faith. The point is that quantum mechanics is just as consistent with this faith as was classical mechanics.

Consistent Quantum Theory

 

[JamieSalaor]

Well yes, that's the thing with solipsism. You can always come up with an argument suggesting it. But nothing in science implies that it's the case. Therefore being a solipsist would be too be a matter of faith. One that seems considerably more unreasonable and just unnecessarily arrogant...

What I take from the quote is the Griffiths is saying that Consistent Histories suggests no reason at all to deny the existence of external reality... But if one were to deny external reality it would be very difficult to convince them otherwise...
Carlo Rovelli said the following about solipsism in an email conversation I had with him

Solipsism is a disease which plagues those who are too insecure to accept the limits of our knowledge

Thanks for everything everyone