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The criterion excludes comparing the strength of criticisms, not comparison altogether. ‘Serious’ could be binary: does the contender solve the same problems, reproduce GR’s successful predictions, and lack a pending criticism that prevents replacing GR?

The wrapper provides no immunity. If X’s flaw defeats the proposed use, that flaw can criticize the new policy too. ‘This bridge design collapses, but keep using it’ is criticised by the danger of collapse. Therefore, not almost any criticized idea becomes adoptable this way.

The wrapper provides no immunity. If X’s flaw defeats the proposed use, that flaw can criticize the new policy too. ‘This bridge design collapses, but keep using it’ is criticized by the danger of collapse. Therefore, not almost any criticized idea becomes adoptable this way.

‘X is true’ and ‘use X for purpose Y while acknowledging that X is not true’ are different proposals. A criticism of X as a true description does not necessarily criticise its bounded use.

This assumes ‘approximation’ means measurable closeness to an unknown final theory. In context, it actually means that GR’s predictions closely approximate observed gravitational behaviour in its tested domains. We can compare predictions with observations without knowing the final theory.

“Serious contender” smuggles comparison of explanations with known flaws back in.

How do we distinguish between serious and unserious contenders?

This seems to create a rewording loophole.

Almost any criticised idea could be made adoptable this way: “X has criticisms, but keep using X”

it’s an excellent approximation

It's an excellent approximation to what? Reality? How do we know that?

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.

By this criterion, it is irrational to adopt or advocate either GR or QM, as they have pending criticisms.

According to every physicist I have heard speak on the matter, GR and QM conflict.

@bart-vanderhaegen has also said to me that GR falsely predicts the orbit of electrons, and QM falsely predicts the mass threshold at which black holes form.

By this criterion, it is irrational to adopt or advocate either GR or QM, as they have pending criticisms.

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.

But #5331 relies on our ability to come up with new options to remain rational in the face of mutually exclusive options.

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.

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.)

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.

Liberty says in a previous discussion that the first quote is “just a cherry picked sentence and it's ambiguous as to the claim you're making. Neither Deutsch nor anyone else who agrees with it interprets the theory in the way you're doing.”

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.

But those quotes aren’t all about HTV.

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 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?”