Litany of Instrumentarski

If my beliefs, by so existing, change the outcome of reality

So, if your writing "here be dragons" on a map results in someone encountering a dragon when traveling to the mapped area (a very popular theme in SF/F), how useful is the concept of reality?

You don't need to reject realism to reject the idea that beliefs can only be reflections of reality, rather than a causal part of it.

You don't need to, no. But the concept of reality is less useful if all you mean by it is future inputs to test the accuracy of your beliefs, as opposed to a largely unchanged territory that you map. If you have to build the proverbial epicycles to keep your belief alive, you might want to consider a simpler model.

The map is part of the territory.

Is this a useful assertion? If so, how?

How accurately does your map represent your map?

Not sure what you mean by this. That beliefs can be nested? Sure. That the term "map" presumes some territory it maps? It sure does, in the realist picture. Hence my preference for the term "model" or even "belief". Of course, a realist can ask something like "but what is your model a model of [in reality]?", which to me is not a useful question if your reality is changing depending on the models.

Not sure how this is related to what I posted. It was about accurate accounting, not accurate reporting of your account to someone who doesn't want an accurate account.

That's a good point. I guess I still have to quite a ways to go to rid myself of the notion of external reality, which I was subconsciously assuming. If belief changes reality, too bad for reality. It's the accuracy of the belief that is important.

if A is true

Note that this statement only makes sense if you already subscribe to physical realism, as it presumes the territory separate from any maps.

If you don't make this assumption, this statement means that "at some point I will acquire evidence confirming the model based on A with very high confidence". The currently available evidence may be against A, however. It happens quite often in physics, though not it trivial ways.

For example, light was believed to be composed of particles, until the Poisson's spot was discovered. There was plenty of experimental evidence for it, too. Afterwards, light was believed to be waves, and there was overwhelming evidence for this, as well. Then the UV catastrophe was deduced and the photoelectric effect was discovered, demonstrating that the question "is light a wave or a particle" has a different answer, depending on the manner of asking. The story is far from over at present.

I wish to believe that I will update my beliefs based on available evidence (a bit meta here).

I don't follow. What computational power do you mean? And what bad black swan bets? A couple of examples would be great.

Interesting. Do you mind elaborating?

I disagree with this modification. The first one explicitly focuses on the causal effect of the belief, but the second one focuses on the temporal successors of the belief. The first is much stronger, more useful, and more general than the second.

I prefer the modification, for some of the same reasons that you disagree with it. That is, because the modification is weaker, less general, actually doesn't serve to convey shminux's position and avoids conflating instrumentality considerations with the anti-realist position.

Specifically, saying this:

If I will find no diamond in the box,

I desire to believe that I will find no diamond in the box;

... does not entail any sort of claim about the distribution of the diamond in situations in which one will not happen to, or expect to be able to, personally interact with the diamond but still care whether diamond containing box are sent to some place. ie. It is technically compatible with:

If Sally will find a diamond in the box but I will never receive any message from Sally or the box after the box arrives at Sally,

I still desire to believe that Sally will find a diamond in the box.

(Or, you know, food rations and a terraforming device for her colonization mission.)

More analogously, you should believe that the proposition "snow is white" is true if and only if believing that snow is white has positive utility.

There is a difference between the proposition being true and believing the proposition is true, right?

The proposition "snow is white" is true if and only if believing that snow is white has positive utility.

That's quite catchy.

I don't believe we are talking about the same thing. I wasn't talking about utility, I was talking about testability. My operational definition of truth is the accuracy of predictions. Except for the "mathematical truths", which are well formed finite strings of symbols.

All the time, don't you think?

You yourself implicitly acknowledge as much when you said that you desire to find diamonds in the box

I never said that. In this example I don't care about diamonds. I desire to believe that my expectations of the number of diamonds will match the reported number of diamonds should, I bother checking. Could be one or could be none, whatever, as long as it matches.