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I also reply that it needs to rank any pair, not every pair.

Why should HTV need to algorithmically rank every pair of explanations to be meaningful?

Because, per BoI, we can’t claim to have understood a computational task if we can’t program it. The formation of rational preferences is a computational task. I say this in my reply.

Not a mathematician but AFAIK, Hilbert basically asked if we could make a machine that answers every math question correctly. The answer to that is ‘no’. But an algorithm for rational decision-making isn’t about that.

I point out that he and I have already discussed that. He has so far ignored the tentative outcome of that discussion, which leaves my stance with zero pending criticisms and his with five (at the time of writing), see #5340.

Related: #5354 and comments.

I don’t care whether people agree with me about this. I care about what’s true, what the ideas imply, as written. Ironically, chapter 1 also says theories can have implications their authors did not intend or may not like (p. 27):

What if you’d rather not know? You may not like these predictions.
Your friends and colleagues may ridicule them. You may try to modify
the explanation so that it will not make them… You will fail.

Citation needed. You of all people should know to cite since you hate when others cite from memory. Don’t be a hypocrite.

I reply:

BoI is full of remarks about preference formation. Doing word searches for “choose between” and “rival explanation”, we can find, for example:

“… we should choose between [policies or theories] not on the basis of their origin, but according to how good they are as explanations: how hard to vary.” (209)

“… how does the ‘dictator’ itself choose between rival explanations …?” (341)

“[The] main use [of experience] is to choose between theories that have already been guessed.” (4)

“The role of experiment and observation is to choose between existing theories…” (32)

I later found more evidence running a word search for the string ‘prefer’:

“Whenever a wide range of variant theories can account equally well for the phenomenon they are trying to explain, there is no reason to prefer one of them over the others, so advocating a particular one in preference to the others is irrational.” (21, emphasis mine)

And chapter 13 is virtually all about forming rational preferences.

Then there’s TCS common-preference finding…

Ben explored and addressed this criticism in more detail, see #5382.

I reply that “Not all programs prompt users for input at runtime”

This is addressed in section 5 of Dennis' paper: The Structure of Rational Thought.

‘How can we rationally proceed when all known ideas have pending criticisms?’
By treating ideas as immutable and discrete, even if content overlaps. For example, as a description of reality, general relativity has pending criticisms. But there are no serious contenders. Instead, take the idea: ‘Although GR has pending criticisms as a true description of reality, it’s an excellent approximation, makes precise predictions, and powers technology such as GPS. So we keep using it until we find a replacement.’ As written, this idea has no pending criticisms, so its advocacy is rational.

Quote missing italics.

I read “two strings” literally. The strings are the only case-specific inputs. A fact read from a database, sensor, or anywhere else is another input, whether or not it appears in the function signature.

No function of those two strings can always provide such a ranking.

The bounty says the code must accept two strings as input. It doesn’t say only or at most or exactly two. But I see now that this may not have been clear – if you think it’ll help, I can edit the bounty to say ‘at least two’.

Also, when I wrote the bounty, I meant input as in ‘part of the function signature’. If the function body later reads from a database or prompts the user for input, that doesn’t in and of itself disqualify the submission.

… we cannot avoid guesswork about which changes preserve meaning …

If a good-faith submission prompted the user for answers about changes in meaning or other creative input (within reason), that also would not automatically disqualify the submission. (The proviso “within reason” matters or else bad actors will simply prompt the user to tell the program which explanation is harder to vary. As with all other bounties, any submission will have to meet not just the bounty terms but survive all criticism it may get.)

Here also, I can edit the bounty to clarify that user input at runtime is permissible.

I hope I’ve addressed all reasons the bounty might not be doable, but let me know if I missed something.

Bulk idea

In #5368, I mean fully new options. Like a new theory in addition to QM and GR. Such a theory is extremely hard to come by.

I reply:

Sometimes it’s *hard* to come up with new options. Like in the conflict between QM and GR. So then we have to choose from existing options because we can’t trivially just ‘be creative’ to make a new one

I give “another argument that rationality isn’t the same as creativity: we can creatively come up with ways to suppress criticism”

I ask: “If HTV is just a feature of explanations but not a criterion to form rational preferences, does that mean we could rationally adopt Persephone over axis tilt?”

The implied criticism is that that is clearly not what HTV is intended for.

As for ambiguity, I don’t see how it’s ambiguous, at least now, given the additional quotes and the fact that chapter 1 is in large part about preference formation, as I say in #5363.

I address the cherry-picking charge now:

… chapter 1 was in large part about HTV as a way to prefer axis tilt over Persephone. That was a central part of that chapter: to present David’s answer to how we can make rational choices, using axis tilt vs. Persephone as an example.

So, far from being cherry-picked, several pages in BoI, almost a whole chapter, are about preference formation using HTV.

I preemptively address that:

Let me state preemptively that I realize these quotes aren’t exclusively about HTV. There are other factors involved in rational decision-making, such as the outcomes of crucial tests (then again, David does link that to HTV in chapter 1). I give these quotes to show that David recognizes and contributes to the problem of how to form rational preferences throughout BoI from various angles.

I reply:

The question of how we can make rational preferences has been a key philosophical problem since antiquity. Saying HTV isn’t for that is frankly a disservice to Deutsch because it demotes HTV from a genuine philosophical contribution to a mere feature of some explanations that we don’t know what to do with.

I reply: “Why care whether explanations have this feature if not to prefer them?”

There’s no contradiction there. It can be both a feature of explanations and a tool to help us make decisions.