(urth) 5HC : Skinner, Turing and yet more Laplace

Iorwerth Thomas iorweththomas at hotmail.com
Wed Feb 16 06:04:23 PST 2005

I'm going to backtrack a bit on this discussion; I've been a a bit out the 
loop due to a horrible flu/cough thing that had me running a high fever 
until yesterday...

>From: maru <marudubshinki at gmail.com>
>Laplace's demon is truly omniscience no?

Only in the sense that if you give him deterministic physical laws and some 
intial conditions, he can calculate everything that follows from them with 
arbtrary accuracy.

>Then he knows you are going to tell me, and has factored that in.
>He will also know that you will ask for an updated prediction.
>That too will be foreseen by his omniscience right?
>Furthermore, he will see you scurrying back to tell me.
>But, omniscient being he is, he can see how many times you will be able to
>upset the temporary equilibrium of my desires, and indeed, when I will 
>begin to ignore
>you (or ask what you are smoking and how can I synthesize suma that?).
>That number being finite, he can easily  work out what my final desires 
>will be, and give the answer
>which will both start the sequence and end it.
>Even better, in a deterministic universe like this, to the Demon, the only 
>unkown will be himself.
>So he can easily choose how he will perturb the universe, and make his 
>predictions on that basis
>or self-fulfilling.

Ummm.  I think I may have botched my presentation of the argument.  You are 
quite right.  _But_, the issue isn't what the demon knows, it's what _you_, 
as the person who has just been given the prediction, are correct in 
believing; the implication being that there's no determinate plan of your 
future actions that you'd be correct in believing if only you knew it.  
Thus, even if your actions are in some sense determined by the laws of 
physics, this isn't quite the same as metaphysical determinism, where you'd 
expect there to be a determinate plan of your future actions that would 
remain correct if you knew it.  I think.

I think I've fatally flawed the whole thing by bringing in the demon, though 
[1].  Originally, it was a large computer, and the result was then 
generalised by replacing the computer with God in an attempt to 
short-circuit the free-will vs. predestination debate.  Barrow's book gives 
a better explanation (mostly by quoting Mackay/Mackie).

There may a small scale analogy of this knd of thing with psychology 
experiments - I imagine that if you're trying to repeat an experiment and 
some of the group are aware of the original results it skews thing somewhat. 
  Maybe someone who knows more than me can confirm/deny this.


[1] It's due to an idea for a 'Black Easter' - style short story I keep 
thinking of writing, hampered mostly by my lack of talent, time and the 
unfortunate fact that I've never read 'Black Easter'.

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