1. Scope There are two arm-waving views often expressed about the relationship between “determinism/causality” on the one hand and “predetermination/predictability in principle” on the other. The first treats them as essentially interchangeable: what is causally determined from instant to instant is thereby predetermined over any period - the Laplacian view....
After trying to discover why the LW wiki “definition” of Reductionism appeared so biased, I concluded from the responses that it was never really intended as a definition of the Reductionist position itself, but as a summary of what is considered to be wrong with positions critical of Reductionism. The...
The test for an unbiased definition of a philosophical position is (surely) that it is equally acceptable to critics and defenders of the position. I think the definition of reductionism in the wiki blatantly fails this test. The same bias is apparent in the old Sequence posting dealing with reductionism....
I have now added a hopefully suitable paragraph to the post.
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.
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.
Thanks, so to get back to the original question of how to describe the different effects of divergence and convergence in the context of MW, here's how it's seeming to me. (The terminology is probably in need of refinement).
Considering this in terms of the LW-preferred Many Worlds interpretation of quantum mechanics, exact "prediction" is possible in principle but the prediction is of the indexical uncertainty of an array of outcomes. (The indexical uncertainty governs the probability of a particular outcome if one is considered at random.) Whether a process is convergent or divergent on a macro scale makes no difference to the number of states that formally need to be included in... (read more)
There are no discrete "worlds" and "branches" in quantum physics as such.
This seems to conflict with references to "many worlds" and "branch points" in other comments, or is the key word "discrete"? In other words, the states are a continuum with markedly varying density so that if you zoom out there is the appearance of branches? I could understand that expect for cases like Schroedinger's cat where there seems to be a pretty clear branch (at the point where the box is opened, i.e. from the point of view of a particular state if that is the right terminology).
Once two regions in state space are sufficiently separated to no longer significantly influence each other...
From the big bang there are an unimaginably large number of regions in state space each having an unimaginably small influence. It's not obvious, but I can perfectly well believe that the net effect is dominated by the smallness of influence, so I'll take your word for it.
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... (read more)
So, to get this clear (being well outside my comfort zone here), once a split into two branches has occurred, they no longer influence each other? The integration over all possibilities is something that happens in only one of the many worlds? (My recent understanding is based on "Everything that can happen does happen" by Cox & Forshaw).
even if in the specific situation the analogy is incorrect, because the source of randomness is not quantum, etc.
This seems a rather significant qualification. Why can't we say that the MW interpretation is something that can be applied to any process which we are not in a position to predict? Why is it only properly a description of quantum uncertainty? I suspect many people will answer in terms of the subjective/objective split, but that's tricky terrain.
you can consider the whole universe as a big quantum computer, and you're living in it
I recall hearing it argued somewhere that it's not so much "a computer" as "the universal computer" in the sense that it is impossible to principle for there to be another computer performing the calculations from the same initial conditions (and for example getting to a particular state sooner). I like that if it's true. The calculations can be performed, but only by existing.
the multiverse as a whole evolves deterministically
So to get back to my question of what predictability means in a QM universe under MW, the significant point seems to be that prediction is possible starting from the initial conditions of the Big Bang, but not from a later point in a particular universe (without complete information about the all other universes that have evolved from the Big Bang)?
There are two arm-waving views often expressed about the relationship between “determinism/causality” on the one hand and “predetermination/predictability in principle” on the other. The first treats them as essentially interchangeable: what is causally determined from instant to instant is thereby predetermined over any period - the Laplacian view. The second view is that this is a confusion, and they are two quite distinct concepts. What I have never seen thoroughly explored (and therefore propose to make a start on here) is the range of different cases which give rise to different relationships between determinism and predetermination. I will attempt to illustrate that, indeed, determinism is neither a necessary nor a... (read 2445 more words →)
After trying to discover why the LW wiki “definition” of Reductionism appeared so biased, I concluded from the responses that it was never really intended as a definition of the Reductionist position itself, but as a summary of what is considered to be wrong with positions critical of Reductionism.
The argument goes like this. “Emergentism”, as the critical view is often called, points out the properties that emerge from a system when it is assembled from its elements, which do not themselves show such a property. From such considerations it points out various ways in which research programmes based on a reductionist approach may distort priorities and underestimate difficulties. So far, this is... (read 1010 more words →)
The test for an unbiased definition of a philosophical position is (surely) that it is equally acceptable to critics and defenders of the position. I think the definition of reductionism in the wiki blatantly fails this test. The same bias is apparent in the old Sequence posting dealing with reductionism. (Some comments called it a “straw man” without spelling out why.)
Consider the definition:-
Reductionism is a disbelief that the higher levels of simplified multilevel models are out there in the territory, that concepts constructed by mind in themselves play a role in the behaviour of reality. This doesn't contradict the notion that the concepts used in simplified multilevel models refer to the actual clusters... (read 1114 more words →)
OK, thanks, I see no problems with that.