Re: [UAI] This is Rich Neaolitan's rsponse to the determinism discussion with Kathy L. Dear Rich,

>...based on everything E that happens up to some point in time, 
>something R ends up happening at the next instant. If that event is 
>not deterministically determined by E, then what does determine it? 
>... something made it happen... ... even if it is some random number 
>generator that determines what happens next ... We conclude that the 
>events up until now were deterministically produced. I have a hard 
>time conceiving of anything else, and I guess Einstein and Jaynes 
>did also. The alternative is that the number just `happens', but 
>what does that mean?

Ah, that is the key question, isn't it?

Many people cannot conceive of things that "just happen", and feel 
that they MUST be "determined" by something.  But scientists have 
looked very hard for something that would predict what happens, and 
the best they can do is probabilities conditioned on actions and 
prior states.

Consider a set of situations that are absolutely identical with 
respect to everything relevant to predicting the future, EXCEPT FOR 
the choice of action performed by You and the actual outcome that 
occurs as a consequence of that action. You are free to actualize any 
action You want to, within the possibilities allowed by quantum 
theory.  Your choice is free in the technical sense that it is 
unconstrained in any way by the laws of physics, and indeed, physics 
doesn't predict any probabilities for it. Given that You have chosen 
a given action, any of the outcomes consistent with that action can 
occur. The outcomes are governed by a stochastic law, in the sense 
that if You are being graded by a proper scoring rule, You would be 
very well advised to predict the probabilities specified by quantum 
theory, because in all of the many, many tests conducted thus far, 
those probabilities have been confirmed to many digits of accuracy.

I too am very interested in the question of what "made" those 
stochastic events occur.  I am also very interested in what if any 
laws of Nature govern the choices of action that are open to You, 
about which current physics has nothing at all to say.  Science's 
current models of Your actions are entirely phenomenological.  We 
don't have any fundamental theories for what kinds of systems can 
make quantum events happen or what constraints there might be on the 
kind of quantum events they can cause.  Many physicists don't believe 
quantum events are real phenomena in Nature, but no one has been able 
to develop a consistent quantum theory without them.

>A philosophical stance on what `just happens' could mean is what I 
>was looking for when I wrote this note.

There is a huge literature on this question. From my reading of it, 
it doesn't seem that anyone is anywhere near resolving the issue in a 
way that would be satisfying to me.  I personally don't have much 
idea what "just happens" might mean.  To me it is untenable to insist 
that Nature "has to" be deterministic because I personally have 
trouble conceiving of anything except deterministic phenomena. 
Nature does what She does regardless of whether what she does is 
something I can conceive of.  Maybe She has some deterministic rule 
for producing pseudo-random numbers, or maybe there is some "truly 
random" process going on.  Either way, the probabilistic predictions 
of quantum theory are stunningly accurate, and if someone is grading 
me for accuracy, I would do well to use them.

>This is why I feel that perhaps humans are too unevolved to grasp 
>determinism/indeterminism. We can grasp just enough to torment 
>ourselves with the notion.

Torment?!?!?!? What could be more fun than a good philosophy debate?

>Just as the we can model more of external reality (assuming one 
>exists) than the amoeba, perhaps some future species will do much 
>better than us.

There are things I understand today that I didn't when I was three. 
There are things humanity understands today that we didn't a century 
ago. Perhaps some day I'll understand this too.  Perhaps some day 
someone other than myself will reach a better understanding, and will 
teach the rest of humanity, and then we'll move on to tormenting 
ourselves over other things.  Or having fun with other things.  Take 
your pick.  :-)

Kathy


