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Viliam_Bur comments on The difference between Determinism & Pre-determination - Less Wrong
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Thanks, I think I understand that, though I would put it slightly differently, as follows...
I normally say that probability is not a fact about an event, but a fact about a model of an event, or about our knowledge of an event, because there needs to be an implied population, which depends on a model. When speaking of "situations like this" you are modelling the situation as belonging to a particular class of situations whereas in reality (unlike in models) every situation is unique. For example, I may decide the probability of rain tomorrow is 50% because that is the historic probability for rain where I live in late July. But if I know the current value of the North Atlantic temperature anomaly, I might say that reduces it to 40% - the same event, but additional knowledge about the event and hence a different choice of model with a smaller population (of rainfall data at that place & season with that anomaly) and hence a greater range of uncertainty. Further information could lead to further adjustments until I have a population of 0 previous events "like this" to extrapolate from!
Now I think what you are saying is that subject to the hypothesis that our knowledge of quantum physics is correct, and in the thought experiment where we are calculating from all the available knowledge about the initial conditions, that is the unique case where there is nothing more to know and no other possible correct model - so in that case the probability is a fact about the event as well. The many worlds provide the population, and the probability is that of the event being present in one of those worlds taken at random.
Incidentally, I'm not sure where my picture of probability fits in the subjective/objective classification. Probabilities of models are objective facts about those models, probabilities of events that involve "bets" about missing facts are subjective, while what I describe is dependent on the subject's knowledge of circumstantial data but free of bets, so I'll call it semi-subjective until somebody tells me otherwise!
Yeah, that's it. In case of quantum event, the probability (or indexical uncertainty) is in the territory; but in both quantum and non-quantum events, there is a probability in the map, just for different reasons.
In both cases we can use Many Worlds as a tool to visualize what those probabilities in the map mean. But in the case of non-quantum events we need to remember that there can be a better map with different probabilities.
Great. Incidentally, that seems a much more intelligible use of "territory" and "map" than in the Sequence claim that a Boeing 747 belongs to the map and its constituent quarks to the territory.
In replying initially, I assumed that "indexical uncertainty" was a technical terms for a variable that plays the role of probability given that in fact "everything happens" in MW and therefore everything strictly has a probability of 1. However, now I have looked up "indexical uncertainty" and find that it means an observer's uncertainty as to which branch they are in (or more generally, uncertainty about one's position in relation to something even though one has certain knowledge of that something). That being so, I can't see how you can describe it as being in the territory.
Incidentally, I have now added an edit to the quantum section of the OP.
I probably meant that the fact that indexical uncertainty is unavoidable, is part of the territory.
You can't make a prediction about what exactly will happen to you, because different things will happen to different versions of you (thus, if you make any prediction of a specific outcome now, some future you will observe it was wrong). This inability to predict a specific outcome feels like probability; it feels like a situation where you don't have perfect knowledge.
So it would be proper to say that "unpredictability of a specific outcome is part of the territory" -- the difference is that one model of quantum physics believes there is intrinsic randomess involved, other model believes that in fact multiple specific outcomes happen (in different branches).
OK, thanks, I see no problems with that.