Re: Time Machines, FTL, and P=NP

James Burns <burns.87@[EMAIL PROTECTED]
> wrote:
> Actually, I do think that my free will would go away in
> certain causality-violating circumstances. But we may not be
> in disagreement (about this point) because we may not be agreeing
> about what free will is, etc.

I think you're right. We agree on what happens, just not on what it means.

I as simply a means for discovering the best way to pursuade someone. You 
see it as, basically, a quantitative difference so large that it becomes 
qualitative. That is, a machine which gives you the perfect means of 
pursuading someone means that you circumvent their free will.

My argument against your position would be that there are *probably* 
situations where a person cannot be pursuaded by any means at your 
disposal. In that case your machine will either fail, meaning they have 
free will, or it will bend their mind, meaning that it doesn't work the 
way that we've discussed.

>> I think there are two different arguments which can be made here,
>> along the lines of the weak and strong anthropic principle.
>> 
>> The "strong" version would be, this wacky crap is nonsensical,
>> therefore causality is required.
>> 
>> The "weak" version would be, this wacky crap is nonsensical,
>> we can't even discuss it properly, so there's no point in
>> discussing what happens because we just can't know.
>> 
>> I agree with you that the "strong" version is kind of a bad way
>> to do things, but I think the "weak" version has some merit.
>> The ideas I've come up with just scratch the surface. Trying to
>> think about the ultimate consequences of causality violation is
>> like Ben Franklin trying to derive the Internet from the results
>> of his kite/lightning experiment. It's interesting to discuss
>> but we shouldn't think that these ideas would necessarily bear
>> out in reality.
> 
> I'm glad you think the strong version of "wacky crap means no time
> machine" is a bad argument. That's actually the one I've seen in
> such discussions more often than not.
> 
> I guess I don't understand your "weak" argument. Discussions
> always start out crude, ill-informed, badly phrased. The
> hope is always that they will become clearer, more useful
> discussions, but, of course, that can't happen if the
> earlier silly discussions don't happen.
> 
> And I don't think I've ever heard "we just can't know"
> without it being closely followed by "well, how could
> we find out?"

Pretend for a moment that we're not talking about time machines, but 
instead about faeries. The discussion is based around the question of what

we could do if faeries exist. Could we build faerie-powered starships? 
Faerie-powered lockpicks? What design would you use to construct a 200 
mile-per-gallon faerie-catalyzed Cadillac?

It may be fun speculation but from a scientific standpoint it's all 
garbage. The term isn't defined well enough to discuss it in any context 
other than fun.

Thus it is with causality, I think. Fundamentally it's outside our 
understanding, so discussion of the consequences is necessarily 
non-scientific.

> I agree with your estimate of how far along
> we are in understanding causality, except that I think
> comparing us to Ben Franklin is much too generous.

Could be, but it's tough coming up with decent analogies!

> My own bet is that the only "application" we will ever
> have is an understanding of why time machines are
> impossible, but that is something I would like
> to see.

It would be interesting. It's often repeated in this group that you can 
pick any two of relativity, FTL travel, and causality. The almost 
universal choice is to pick relativity and causality, but the reason for 
picking causality isn't always rigorous.

-- 
Michael Ash
Rogue Amoeba Software