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lavalamp comments on The Apparent Reality of Physics - Less Wrong Discussion

-3 Post author: ec429 23 September 2011 08:10PM

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Comment author: lavalamp 23 September 2011 10:34:16PM 2 points [-]

Inasmuch as a mistaken simulation of B is a simulation of "B plus the arbitrary law that 'foo happens at time t'", then yes, B' exists platonically. Consider B = "x'' + x = 0, x(0)=x'(0)=0", B' = "x'' + x = δ(x-1), x(0)=x'(0)=0". These are both coherent mathematical models; they model different things, but B' still exists platonically. A cosmic ray could indeed make an ostensible model of B model B'.

Does your model differ from "Everything that could exist, does"? I can imagine setting up a simulator for a universe just like ours, except that every time a planet coalesces, it's spontaneously replaced with a kangaroo. Does the fact that I can describe such a system imply (to you) that it actually exists? That without me even actually making a simulation of it, multitudes of kangaroos are each experiencing a few brief seconds of asphyxiation around their stars?

It's observationally equivalent to the hypothesis of manifest reality, but strictly simpler (it removes unnecessary ontological elements, and converts uncertainty about physical law into indexical uncertainty). Like Many Worlds, really.

Well, it's making me think, anyway.

Comment author: ec429 23 September 2011 11:04:46PM 1 point [-]

Does your model differ from "Everything that could exist, does"?

Not quite. Every mathematical structure (strictly, every syntactic language) that could exist, does (and causes its corresponding apparent physical reality to appear to exist) - so the kangaroos do indeed exist (and did so even before you thought of them). After all, how could you have an effect on the kangaroos merely by simulating them? (I maintain that the causal relation runs from the kangaroos to you, not the other way round).

It may well be impossible to devise an example of something that doesn't exist (because, if we can think about it, it is modellable), but that doesn't mean to say that things that don't exist, um, don't exist... I mean, {X : not exist(X)} need not be empty, it's just that we can't exhibit any of its elements. It might be provably empty, but I have no proof here and can't imagine what form one would take.

Also, you have to be a bit careful about the causal relations; if you start thinking of them as one formal system modelling another, you get into Gödel-space. Hence the Syntacticism post; I think it's accurate to say that one formal system models a quotation of another, but I'm not sure of that.

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