ygert comments on Harry Potter and the Methods of Rationality discussion thread, part 19, chapter 88-89 - Less Wrong

12 Post author: Vaniver 30 June 2013 01:22AM

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Comment author: ygert 30 June 2013 08:47:10AM *  5 points [-]

Are you objecting to a time travel argument because it is circular?! Of course it's circular, it's time travel. That's the thing about time travel, it makes causal circles. That's why it drives you insane to think about it.

Comment author: Baughn 30 June 2013 05:45:15PM 3 points [-]

It's about fixed-point solutions.

Harry got "Do not mess with time" because he was willing, in that case, to send the same message back. If he hadn't been, he never would have received that message in the first place.

Comment author: Decius 01 July 2013 12:08:00AM 1 point [-]

If Harry had been willing to write "101x101" after receiving "do not mess with time", he would have solved NP=P?

Comment author: Baughn 01 July 2013 02:48:05PM 2 points [-]

If he had been willing to do that, he wouldn't have received "do not mess with time".

Though I notice I'm confused as to how, exactly, the universe can figure out he'd create a paradox in this situation without actually running the computation to see what happens. Probably it can't. Probably time-travel is hilariously unethical.

Comment author: Decius 01 July 2013 06:15:01PM 1 point [-]

The universe isn't limited to object-level proofs that exist in the universe, I guess. Perhaps the universe has access to the list of everything which is true about the universe?

Comment author: Baughn 01 July 2013 07:58:07PM 0 points [-]

Well, how do you make that list?

Comment author: Decius 02 July 2013 04:08:40AM 0 points [-]

I don't. It's not accessible from the object level, or any combination of first-order meta levels. it takes at least a second-order meta (2°meta:1°meta::1°meta:object) to create such a list, and I can't even begin to explain what second-order meta means.

Comment author: Baughn 02 July 2013 10:27:33AM 0 points [-]

All right, so long as you realize that means you can't evaluate whether or not such a thing is possible. :-)

Argument from confusion doesn't work.

Comment author: Decius 02 July 2013 10:18:25PM 1 point [-]

Well, I can consider the analogous situation where time travel is repeated in an attempt for Emperor Yingling of Scandinavia to convince all of his respective kingdoms to adopt ultimogeniture secession before he dies, so that his youngest son won't have to fight secession wars as he tries to expand into Rus while defending Aragorn from upstarts who object to imperial expansion by marriage.

I don't think that save-scumming is immoral because simulations are dying, although I am receptive to arguments that it is immoral because it breaks the rules.

Comment author: Eugine_Nier 02 July 2013 12:37:30AM 0 points [-]

I think you're inappropriately anthropomorphizing the universe.

Comment author: JoshuaZ 02 July 2013 12:39:44AM 2 points [-]

Given that this universe settled on an explicit message about not messing with time, and given how much magic apparently involves naive mental entities, it seems like anthropomorphizing the laws of physics is a much more useful heuristic in the HP universe than it is in ours.

Comment author: Baughn 02 July 2013 10:31:16AM *  0 points [-]

I was thinking about how I'd implement HPMoR-style time-travel in a turing machine, actually.

It goes something like this:

  • Compute every possible future that doesn't contradict something in the fixed past, including loops.

  • Whenever you find a paradox, delete that timeline.

  • Repeat.

That would generate a story we could read, no problem. It wouldn't generate anyone who actually experiences paradoxes, either; to the degree those actually exist, they never get out of the subatomic level. It's not clear to me whether or not this results in a universe that can usefully be experienced, though, or (more to the point) whether your future experiences match up with the type of experiences you remember.

..kind of odd.

Comment author: Eugine_Nier 01 July 2013 01:56:46AM 0 points [-]

I suspect he would have had an unfortunate encounter with someone else's stable time loop.

Comment author: DanielLC 30 June 2013 05:35:41PM 1 point [-]

It's not entirely obvious what causes a given stable time loop, but that doesn't mean there is no way to predict it. Even if it's random, it has to have some kind of probability distribution. Time loops isn't an excuse for an author to do whatever they want. At least, not if they want it to take place in a universe based on rules and not narrative causality.