Graduate Consistent Histories solipsism?

[JamieSalaor]

So, would you say even with the 1995 formulation of CH they were mistaken to accuse it?

 

[Morbert]

yes

 

[JamieSalaor]

I was looking at more recent work by them and they don't seem to have accused CH since.
Nor have any other authors...
So maybe more people are coming to realize that it isn't solipsism
Thanks for this by the way, you've been loads of help!

 

[JamieSalaor]

Does Solipsism of the moment link to the idea put forward in that other forum about us not being able to determine the age/existence of dinosaurs?
I assume you believe this isn't the case and that dinosaurs obviously did exist 66mya?

 

[AlexCaledin]

- I believe dinosaurs were briefly simulated in the Great Computer)

(our unruly brains - that's the only physical thing which is real hard to compute)

 

[JamieSalaor]

I think you've cracked it mate

 

[Morbert]

Does Solipsism of the moment link to the idea put forward in that other forum about us not being able to determine the age/existence of dinosaurs?
I assume you believe this isn't the case and that dinosaurs obviously did exist 66mya?

Yes

As soon as we decide to believe in dinosaurs, we have left the solipsist position. I.e. We have decided to interpret some propositions about the past as factive.

Dowker and Kent argue that we are forced back to the solipsis position if we accept CH.

"If one accepts the formalism as it stands, and introduces no historical actual facts, one seems to be led toward solipsism of the present, since it is unlikely that any past event can be described in every consistent set, and each consistent set gives an equally valid description of the past."

Basically, they are arguing we can always eliminate a fact about the past by selecting a consistent set incompatible with the fact we want to eliminate. But the selection of a consistent set is not a selection of facts that exists. It is instead the selection of a set we wish to use to reason about some facts.

 

[JamieSalaor]

I don't understand how it's actually solipsist.
It seems as if you have a choice in the development of frameworks whether or not you want to deny the existence of dinosaurs or anything else.
But since that's a really backwards thing to do you won't do it...

Do you think they've misunderstood CH. Or are unnecessarily making it seems bad..

Would you say CH even at all disregards real historical facts? I don't think that's reasonable..

 

[JamieSalaor]

It doesn't seem as if the CH interpretation requires you to deny historical facts at all.
It just says you could, but that would obviously be wrong. So you don't

 

[PeterDonis]

Would you say CH even at all disregards real historical facts? I don't think that's reasonable..

What are "real historical facts"? Remember that we only directly experience our present, not our past; we directly experience having memories of a past, or looking at records that we interpret as evidence of something having happened in the past, but that's not the same as directly experiencing, now, an event in the past.

From a CH point of view (or at least the CH point of view being taken by Dowker and Kent), however, interpreting our present experience of memories or looking at records as evidence of particular past events is only a valid inference, strictly speaking, if all consistent histories that contain those present experiences also contain the past events being inferred from those experiences. But that's not the case. There will be consistent histories containing the same present experiences, but which don't contain the past events we infer from those experiences, because the present experiences are due to some kind of astronomically unlikely quantum fluctuation that basically rewrote all of our memories and records to indicate a past event that didn't actually happen.

I don't think one is required to adopt such a point of view if one adopts the CH interpretation, but one cannot rule it out by any logical argument, since such astronomically unlikely quantum fluctuations are present in the math of QM.

 

[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?