Dear Richard,

Perhaps I understand better now the root of our disagreement. It seems to have something to do with whether the definition of locality refers to actions of an agent on one side having consequences on the other side, or whether it refers to events on one side having consequences on the other side, where events may include random…[Read more]

I disagree that the condition that X has no influence on B can be expressed as Prob(B/X,Y)=Prob(B/Y): that condition merely expresses the inequality of two general probabilities, each of which may be used to infer a (different) chance of an outcome event being of type B (there is no unique chance of an event’s being of type B in this case—see my…[Read more]

Dear Bob,

Yes, let’s agree to disagree. Thank you for the discussion.

All the best, Roderich

Dear Roderich,

Thank you for your explanation. I think your “English property” would be what I call a “quasiclassical property/projector” using the language of Gell-Mann and Hartle. On the other stuff I think we will just have to agree to disagree. I once told d’Espagnat that the simplest explanation for why those mysterious superluminal…[Read more]

Dear Richard, (in response to your #1901)

I agree that “we can’t decide whether B is a function of events on all or part of H without applying some theory” if “theory” means laws governing a possible reality (i.e., what I called a “scenario” in my paper). Quantum theory is often understood as not talking about reality but only about empirical…[Read more]

Dear Bob, (at #1900)

Yes, it would good to find out what exactly we disagree about. So let me answer your questions about my position. By “English properties” I did not mean macroscopic properties. In your example, I assume that S is 1-dimensional. I agree that with “cat is alive” is associated a (high-dimensional) subspace A of the Hilbert space…[Read more]

Roderich, (in response to your 1898)

We can’t decide whether B is function of events on all or part of H without applying some theory. Simply observing relative frequencies of 1 in a sequence of supposedly similar sets of events can’t exclude failure of a corresponding functional relation in unobserved sets.
If we apply quantum theory, we see tha…[Read more]

Dear Roderich,

In response to your #1899. Thanks for your clarification, but I am still unsure where you stand. Let us start with ‘English’ properties, by which I think you mean macroscopic properties. Will you allow me to assign things like “pointer is directed at the symbol L on the box” to a Hilbert subspace (of necessarily enormous…[Read more]

Dear Bob,

Thank you for your replies #1860 and 1861. There are two relevant meanings of the word “property”: let me call them “English property” (the ordinary meaning of “property” in English) and “quantum property.” An English property of a system is something that a system either has or has not, while a “quantum property” of a system is a…[Read more]

Dear Richard (at #1859 and 1894),

I like that you point specifically to the step in the reasoning that you are objecting to. That helps for a good discussion.

I see that the word “pre-determines” has connotations that are irrelevant to the argument. For my purposes, “x pre-determines y” just means “y is a function of x.” It is not necessary to…[Read more]

Dear Roderich,

In section 7 of your paper you lay out an argument as to why (L) implies (R1). Here’s why that argument fails to establish its intended conclusion.
I quote the crucial steps from your paper:
“Assume locality. Alice’s experiment takes place in a space-time region A and Bob’s in B at spacelike separation. There is a Lorentz frame i…[Read more]

Dear Roderich,

In section 7 of your paper you lay out an argument as to why (L) implies (R1). Here’s why that argument fails to establish its intended conclusion.
I quote the crucial steps from your paper:
“Assume locality. Alice’s experiment takes place in a space-time region A and Bob’s in B at spacelike separation. There is a Lorentz frame i…[Read more]

Hey, I agree with Howard about something! Namely: the actual EPR paper is quite convoluted. Re: Matt’s #s 4 and 5, I actually think somebody would have a much easier time reconstructing a rigorous version of EPR+Bell by reading Bell alone (and perhaps the cited Einstein!) than by reading Bell plus EPR. Bell’s recapitulation of the EPR-ish…[Read more]

Well of course if you use different assumptions you can do the EPR argument very simply. The challenge is to read the EPR paper, and try to extract a rigorous argument from it, phrase by phrase, word by word, even. Or maybe I don’t understand what you mean by “primitive concepts”.

Glad you agree with my own first paragraph. But I disagree with…[Read more]

Hi Howard,

I agree with your first paragraph.

“Local determinism” (LD) indeed encompasses everything you need for the 1964 Bell’s theorem [minimal]. I was attempting to reserve DL just for the formulation of locality once determinism is already in place. I think it makes phrases like “any reasonable “localist” notion that manifestly reduc…[Read more]

Matt

Sure, I totally agree that the DAG intuition is why Bell thought he had proven determinism from predictability. But I guess we both agree that it would be completely unreasonable to allow that as an implicit assumption in a theorem, since orthodox quantum theory violates it. As I’ve always said, I am interested in Bell’s *theorem* of 1964,…[Read more]

Hi all,

I can’t help wondering if a few tweaks to Howard’s nomenclature might help bridge much of the remaining divide. How about something like this:

Deterministic Locality (DL): A somewhat clunky name for Travis’ equation 3.
A 1964 Bell’s theorem: any theorem of the form “There exist quantum phenomena for which there is no theory satisfying…[Read more]

Howard #1872,

Of course nobody would have put it quite like I did in 1964. But the DAG is an attempt to formalise fairly natural and long-standing way of thinking about causality (as evidence: two different formulations based on functions and probabilities respectively, turn out to be completely equivalent), the basic ideas of which (e.g.…[Read more]