There are two issues, what I view as non-standard language use, and what I view as a category error.
You can use the word ‘testability’ to signify a binary relation, but that’s not what people typically mean when they use that word. They typically mean “possibility Nature can tell you that you are wrong.”
So when you responded many posts back with a claim “MWI is hard to test” you are using the word “test” in a way probably no one else in the thread is using. You are not wrong, but you will probably miscommunicate.
An empirical claim has this form: “if we do experiment A, we will get result B.” Nature will sometimes agree, and sometimes not, and give you result C instead. If you have a list of such claims, you can construct a “story” about them, like MWI, or something else. But adding the “story” is an extra step, and what Nature is responding to is not the story but the experiment.
The mapping from stories to lists of claims is always always always many to one. If you have [story1] about [list1] and [story2] about [list2], and Nature agrees with [list1], and disagrees with [list2], then you will say:
“story1 was falsified, story2 was falsifiable but not falsified.”
I will say:
“list1 was falsified, list2 was falsifiable but not falsified.”
What’s relevant here isn’t the details of story1 or story2, but what’s in the lists.
When I say “MWI is untestable” what I mean is:
“There is a list of empirical claims called ‘quantum mechanics.’ There is a set of stories about this list, one of which is MWI. There is no way to tell these stories apart empirically, so you pick the one you like best for non-empirical reasons.”
When you say “MWI is testable” what I think you mean is:
“There are two lists of empirical claims, called ‘quantum mechanics’ and ‘quantum mechanics prime,’ a story ‘story 1’ about the former, and a story ‘story 2’ about the latter. Nature will agree with the list ‘quantum mechanics’ and disagree with the list ‘quantum mechanics prime.’ Therefore, ‘story 1’ is testable relative to ‘story 2.’”
That’s fine, I understand what you mean, and I think you are right, up to the last sentence. But I think the last sentence is a category error.
Because you are equating lists of claims with stories, you are carrying over the testability property of the list ‘quantum mechanics’ to your favorite story about this list, ‘MWI.’ But there is an infinite list of stories consistent with ‘quantum mechanics’. I can replace ‘MWI’ in your argument with any other consistent story, including those involving the flying spaghetti monster, etc.
Then you get unintuitive statements like ‘the flying spaghetti interpretation of quantum mechanics is testable relative to X.’ This is a sufficiently weird use of the word “testable” that I think we should not use the word “testable” in this way. And indeed, I believe the standard usage of the word “testable” is not this.
There are two issues, what I view as non-standard language use, and what I view as a category error.
You can use the word ‘testability’ to signify a binary relation, but that’s not what people typically mean when they use that word. They typically mean “possibility Nature can tell you that you are wrong.”
So when you responded many posts back with a claim “MWI is hard to test” you are using the word “test” in a way probably no one else in the thread is using. You are not wrong, but you will probably miscommunicate.
An empirical claim has this form: “if we do experiment A, we will get result B.” Nature will sometimes agree, and sometimes not, and give you result C instead. If you have a list of such claims, you can construct a “story” about them, like MWI, or something else. But adding the “story” is an extra step, and what Nature is responding to is not the story but the experiment.
The mapping from stories to lists of claims is always always always many to one. If you have [story1] about [list1] and [story2] about [list2], and Nature agrees with [list1], and disagrees with [list2], then you will say:
“story1 was falsified, story2 was falsifiable but not falsified.”
I will say:
“list1 was falsified, list2 was falsifiable but not falsified.”
What’s relevant here isn’t the details of story1 or story2, but what’s in the lists.
When I say “MWI is untestable” what I mean is:
“There is a list of empirical claims called ‘quantum mechanics.’ There is a set of stories about this list, one of which is MWI. There is no way to tell these stories apart empirically, so you pick the one you like best for non-empirical reasons.”
When you say “MWI is testable” what I think you mean is:
“There are two lists of empirical claims, called ‘quantum mechanics’ and ‘quantum mechanics prime,’ a story ‘story 1’ about the former, and a story ‘story 2’ about the latter. Nature will agree with the list ‘quantum mechanics’ and disagree with the list ‘quantum mechanics prime.’ Therefore, ‘story 1’ is testable relative to ‘story 2.’”
That’s fine, I understand what you mean, and I think you are right, up to the last sentence. But I think the last sentence is a category error.
Because you are equating lists of claims with stories, you are carrying over the testability property of the list ‘quantum mechanics’ to your favorite story about this list, ‘MWI.’ But there is an infinite list of stories consistent with ‘quantum mechanics’. I can replace ‘MWI’ in your argument with any other consistent story, including those involving the flying spaghetti monster, etc.
Then you get unintuitive statements like ‘the flying spaghetti interpretation of quantum mechanics is testable relative to X.’ This is a sufficiently weird use of the word “testable” that I think we should not use the word “testable” in this way. And indeed, I believe the standard usage of the word “testable” is not this.