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DanielLC comments on Completeness of simulations - Less Wrong Discussion

1 Post author: RolfAndreassen 24 August 2012 10:44PM

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Comment author: DanielLC 25 August 2012 05:15:03AM 1 point [-]

I don't understand why that follows; can you elaborate?

A sufficiently nice function is mathematically guaranteed to have at least one fixed point where f(x) = x. We need to make some assumptions to make it nice enough, but once we do that, we just set x as the hypothetical GLUT output, and f(x) to the GLUT output of the subject's reaction to x, and we know there's some value of x where the GLUT output of the reaction is the same as what the subject is reacting to.

Additionally, "at least one fixed point" seems distinct from "we can construct X for all situations".

f is the situation, and the fixed point is what you're calling X. Also, I'm not sure if there's a method to construct X. We just know it exists. You can't even just check every value of X, because that only works if it's discrete, which means it's not sufficiently nice.

Comment author: RolfAndreassen 25 August 2012 07:47:36PM 0 points [-]

Thanks for the elaboration; this is a very interesting point that I wasn't aware of. But it does seem to rely on the function having the same domain as its range, which presumably is one of the assumptions going into the niceness. It is not clear to me, although perhaps I'm just not thinking it through, that "future movements of quarks" is the same as "symbols to be interpreted as future movements of quarks".

Comment author: DanielLC 26 August 2012 02:31:18AM 0 points [-]

You could think of it as x is the GLUT output, f(x) is the subject's response, and g(f(x)) is the GLUT's interpretation of the subject's response. f maps from GLUT output to subject response, and g maps from subject response to GLUT output. f and g don't have fixed points, because they don't have the same domain and range. f∘g, however, maps from GLUT output to GLUT output, so it has the same domain and range. I was just calling it f, but this way it might be less confusing.