Harry Potter and the Methods of Rationality

Harry Potter and the Methods of Rationality
Petunia married a scientist. Now rationalist!Harry enters the wizarding world armed with Enlightenment ideals and the experimental spirit... Common review: 'I thought I'd read everything in HP fanfiction, but this is new.'
Harry Potter - Rated: T - English - Drama/Humor - Chapters: 17 - Words: 95,463 - Reviews: 2981 - Updated: 4-24-10 - Published: 2-28-10 - Harry P. & Hermione G.

READ IT. It's both hilarious and thought provoking. And it's not Harry Sue. I'll edit more description up here when I'm not in the middle of a debate about the nature of time travel involving stable timeloops. Yes, scarily enough, the crazy stuff following this is directly related to the story.

the abcdabcda... thing was just my way of making as few assumptions as possible. I don't think the universe would be very happy with such a result, but I do not assume such a thing. It could work perfectly well with an additional temporal axis. It'd graph out something like a sine wave.

I guess what your missing is that you seem to think that events need to be stable along a single iteration that continuously repeats itself. Neither Harry, nor you, considered that this is not necessarily true. Indeed it would take one HELL of an experiment to determine either way. IF such an experiment were possible. I think it an untestable (or at least untested) hypothesis and so do not assume it axiomatically.

Alternatively, all of this could be wrong and the Time Turner simply abuses the existance of an infinite multiverse to deposit the user into the correct universe.


The reason that I don't like your scheme of "put something different down on the piece of paper" without any plan on how to pick what to put down is this: What if seeing 3 makes you write 5, then seeing 5 makes you write makes you write 3. Or what if you decide beforehand to use only even numbers, which wouldn't work because the ONLY even prime is 2, and you need a pair of 3 digit primes. Basically, at that point, solution space opens up to include ANY random stable timeloop of events consistent with the initiating factor. In fact, the most likely outcome is that some random action on your part breaks the time machine, as almost any event that breaks machine will cease to create another iteration of the loop. That, or you do the math wrong when you do your double check, and accept an incorrect answer as correct.

The reason I mentioned "blank paper" an called it an error message was in reference to

"If Harry opened up Paper-2 and it was blank, then he would write "101 x 101" down on Paper-1, fold it up, study for an hour, go back in time, drop off Paper-1 (which would thereby become Paper-2), and head on up out of the cavern level to join his dorm mates for breakfast."

and

"And if Paper-2 said 997 x 997, Harry would leave Paper-1 blank."

I was refering to allowing any state of a series of different iterations which have the initial same input and final output as an error, because that was exactly what you were argueing against happening


Another factor to consider is that you assume that "the universe pushed back" whereas all we know is that some unknown factor or factors resulted in DO NOT MESS WITH TIME being selected from solution space.

 

Yes, I'm saying that there is no way to TEST that this sort of change could not be achieved without being in one of the iterations in which the changover occurred, which is infinitely unlikely compared to the infinite iterations in which the time loop is self sufficiently stable.

In fact, I had already allowed for your hypothesis. That was option A: all events past and future are set in stone. The universe is a static 4 dimensional object. Free will does not exist.

 

From the prior thread:

---

What you seem to be missing is that your assumption that those iterations are genuine, rather than just some linguistic construct we might be able to use to reason about what the end result would be, is completely unjustified. See above: it leads directly to the possibility of changing history, which is against what we see in canon.

So what? Unless you think the universe can actually "get stuck" in a loop, never progressing beyond a certain point, that won't happen. And it can only "get stuck" if it's possible to rewrite history.

Again, so what? If there is only one self-consistent timeline, that literally can't happen because the only self-consistent result is that you receive the correct answer in the first place.

Again, if there is only one self-consistent history, it can't happen because you received information from your future self.

 

And what I'm saying is that I can't think of a single experiment to prove or disprove A or B

(For reference)
Take for instance the canon time when Harry saved himself from the Dementors: there is no possible way that could have occurred unless
A. everything that has happened and will happen is already set in stone, choice does not exist, the universe is a static four dimensional object
or
B. There was a previous iteration, the "first" iteration and Harry died. Then someone, probably Hermione, went back in time and saved him ... forming an unstable timeloop because now she wouldn't go back in time. It keeps oscillating between the two possibilities until a loop arrives that involves Harry going back, eventually a loop n occurs where loop n+1 is the same as n aka Harry goes back and saves his past self who goes back in time and saves his past self. If loop n=n+1 then loop n=n+1=n+2=n+3=n+4=n+5 ... and a stable timeloop is born



And when I say that under A you can't change the future either: recieving a note from the future means that regardless of what you do or want, you WILL travel through time and deliver the note. (Or at least someone will, I don't feel like going through it). And we have no reason to assume that the nature of time across the universe is different during a time-travel event: thus, being unable to change your future WITHIN a time-travel event, makes it highly unlikely that you can change the future OUTSIDE of a timetravel event either.

actually, let me revise that: the existance of prophecies adds some slight bit more weight to A, but there are mechanisms under B that could achieve the same effect.

 

No your assumption is that they are NOT genuine. I simply say that I cannot prove or disprove this and include both possibilities within my range of possible results.


I tend to write more about them being real because there is simply more to write. All you need to say for Option A is that events happen as the 4d structure dictates.

--edit: I'm going to bed now so I'll end this conversation with a vague, self-referential statement involving your mother smelling of elderberries

 

You just got done claiming that in my experiment, you'll get some sort error condition rather than the correct answer. Say you strengthen the experiment by resolving to put only even numbers if the answer you receive is wrong, to purposely try to "miss" the right answer. Then if you are actually able to perform it, a set-unique-timeline always produces the right answer anyway. That's very experimentally distinguishing.

 

Ok, one last post, then sleep. The problem is that you recieve a result that is due to some unexpected underlying factor or factors. The result being: "DO NOT MESS WITH TIME". This result neither confirms nor denies either hypothesis and furthermore strongly suggests that further experiments would not be wise.

 

First: "experimentally distinguishable" is not "we already have experimental results to distinguish them." (Though if we're talking about the fic rather than canon, we have the latter as well.)

Second: We began talking about the intent of Harry's scheme, how it was supposed to work, and what canon examples of time travel might mean regarding it or small variations, including the "put anything different on a wrong answer" one. That the universe produced the unexpected result of "fuck off" (paraphrasing) is outside that particular discussion because Harry never actually did that.

Third: If you want to talk about what the fic results mean, then it is actually evidence against your model of time travel. Under your looped-rewriting model, Harry's experiment must produce the right answer: it just loops until it hits upon the right one, brute-force style. Since Harry's scheme failed, your model is wrong*. On the other hand, a single unchangeable time-line is consistent with the result we see in the fic, though to actually support it in any way more than a failure of an alternative, we'd need more evidence.


* Unless of course someone (incl. people who design time turners) explicitly put something like that in to prevent abuse, without it being a fundamental limitation of time travel in that universe. Or a million and one other factors that could also be going on--but hey, we're talking about evidence, not absolute conclusions.

 

Or the universe is somewhat sapient and doesn't like someone fucking with it.

Or even as the loop went on, the world got funky, and Harry wrote "don't play with time travel" in order to stop it.

 

Yes. But again, we're talking evidence, not absolutes. And both of these are unlikely. In the latter possibility you give, the loops already had a terminating condition that was guaranteed to be reached (and Harry could have skipped to it if he felt like it).

 

no, they aren't unlikely, especially with previous hints in other chapters about the universe being more complex than human can fathom.

Also, Harry couldn't have skipped to it if he felt like it, as he needed to be 'shaky' from the start, and he had his whole plan set up.

Harry had to see the message in order to write it in shaky handwriting

 

Yet we just fathomed those possibilities. Or in other words, it can't be ineffable if you're effing it.

I don't understand what you're referring to. He didn't need to use shaky handwriting to end the loops if genuinely different loops were what was going on in the first place. And if it was his own message because the universe was going haywire, then it would have been much more likely that he would convey more information about what happened. He certainly would have tried his best to--that's part of his character in this fic.

 

There is a difference between understanding that you might not, ever, be able to understand something, and beginning to understand that thing.

Because in order for Harry to have written the message in shaky handwriting, he must have either seen the message once before (probably a bloody one), decided that he better be clear about the danger, write 'DO NOT MESS WITH TIME' with fear in his heart and big shaking, and then next loop will have a lesser shaking, and then current stable loop will have only slight shaking at the implication.

 

Yes, and both of the possibilities you proposed would be understable. You can't support some strange explanations by saying that the universe is unfathomable by human minds. That makes no bloody sense--if it's unfathomable, any explanation you could produce would be automatically wrong, including the ones you just gave.

Probably bloody? The shakiness is probably from some messy, gory end, rather than (say) him trying to force himself into continuing the experiment and failing... or any other non-bloody possibility?

That aside, whatever the actual details were there doesn't change the fact that you're postulating an ad hoc, extra factor just to preserve a particular theory of time travel. That you need to do so makes it a loser in regards to the evidence.

 

All evidence from canon points to this conclusion. Free will is absolutely non-existent in canon, everything is deterministic.

Granted no experiments were ever done to try and prove otherwise, but considering this is exactly what everyone believes and how it is showed in the books, it's a pretty good idea to assume that this is the way it is.

Of course Less Wrong is writing fanfiction and is able to change these things, but in the canon HP universe free will and probably even conscious thought are nothing more than illusions. In that case, you're just a bunch of pieces of matter moving along in a set path that's been unchanged since the formation of the universe. Not even magic can change this apparently universal truth.

 

LINK

Plus, a more layman's explanation.

Thought these two posts might be of use and/or interest to people in this thread. Especially in regards for what this means for the nature of time.

 

What extra factor am i postulating?

I am just trying to explain the shaky handwriting, and the fact that he wrote in it pretty much the opposite of what he wanted to write.

To me, your theory seems to need a lot more postulation.

Vander: possibly, but that makes for an awfully horrible setting to write in.

EJ: interesting, and i probably didn't get a tenth of that.

 

I think you've a broken notion of 'free will' if it is incompatible with determinism. Specifically, you would need to be a mind-body dualist in order for arguments against "determinism+free will" to not equally well cut against an indeterministic universe. Without dualism, they're all just variations of "oh noes, the physical universe forces me to do this because I'm part of it," which is equally true in an indeterministic, but not mind-body dualistic, universe.

Not much. If QFT is correct, then CP-symmetry violation is equivalent to T-symmetry violation. Thing is, the possibilities discussed here are far outside what would be expected from QFT.

The earlier rewrite-history-time-loop theory of time travel predicts that Harry gets the correct factorization result. Since he didn't, you need an extra layer to explain the result while keeping that theory. The extra factor would be whatever is making the universe extra-special-scary FUBAR, which was not part of the original theory, and hence is an ad hoc addition to save it.

It doesn't mean that it can't be right, of course, but I've already covered that.

Canon time travelers never changed their past experience; all we ever see is a self-consistent, single history. Thus, I postulate that there is only that self-consistent, single history. That's it. I postulate quite literally nothing more than we observe in canon.

It is you and Mastigo that make up additional mechanisms about enumerable time loops that rewrite history but eventually stabilize to produce the result... except when they need to destabilize in just the right way first, as you have it.

And the further irony is, Mastigo believes that the two possibilities are not experimentally distinguishable--but then the former would be the clear winner, in as much as it is never reasonable to postulate more than necessary. (Though personally, I'm not convinced that they really are experimentally indistinguishable, cf. above discussion.)

 

Your body is made up of matter and energy. If you cannot change the past with time travel then by definition you have no control over your own actions. Conscious thought is essentially nothing more than an illusion brought about by the matter in your head.

It's not so much of an excuse to do bad things as it is that you could technically develop some sort of machine to predict exactly what is going to happen in the future based entirely upon the position of everything now. Granted it would take an absolutely ENORMOUS amount of computing power to do so, but it should technically be possible.

 

'You' are physical subsystem of the universe, which does determine 'your own actions' to some extent (how much depends on circumstance). Thus, even in a deterministic universe, I would still be in control of my own actions by this very straightforward definition. So which definition are you using, exactly, that leads you to the contrary conclusion?

Why is it in an illusion? 'Illusion' implies that there is a genuine article that this falls short of. You don't specify what would be 'non-illusory' conscious thought, so I have no reason to agree that it is an illusion.

On the contrary, 'consciousness' is typically taken to mean awareness of the self, which I interpret as having a mental model of the self. But this is quite independent of determinism; mental computation corresponds (in some nontrivial and ill-understood way) to physical processes, but there is no reason that those processes cannot encode a model of the self. So again: what definition are you using that leads you to believe otherwise?

The hypothetical that a mental process (corresponding to some physical process) that decided something is reproducible by some other means does not change the fact that it was performed by some physical system that is you, and thus was still your decision.

 

You're dealing with insufficient data and the inability to test anything experimentally.

No rational conclusion can be reached.

So unless Less Wrong provides further data, then you are arguing simply for the sake of argument.

 

Harry just did an experiment for us. Not the one he intended to perform, certainly, but an experiment nonetheless.

An example of a rational conclusion: attempts at creating iteratively changing time loops fail. Because, you know... that's what happened.

Then we can further argue about why they fail, such as (1) they can't happen because the the way the universe works ensures that, as I've argued, or (2) they create increasingly unstable loops of horribleness that eventually spook the time traveler into aborting the experiment, as Arkeus proposed. I see the former as more rational because the latter implies that a sufficiently deranged time traveler can destroy the universe with a time turner. All he or she has to do is not care that the universe is going FUBAR.

 

Or Harry got caught by McGonagall and she threatened to expel him.

 

Sure, it's possible. There are, like I said previously, a million and one other possibilities. That has absolutely nothing to do with whether we can judge a specific explanation A better or worse than some other specific explanation B, which is just what we were doing.

 

Yes, but you judge your explanation based on nothing but your preferences.

What Harry did *should* have given results- unless something got in the way.

We can theorize on what could get in the way, or if Harry's theory was completely unfounded, but we can't be sure.

And, whatever theory we take, we have to take *everything* into account.

The problem here is that Harry in canon couldn't have survived without future Harry helping him. Which can of invalidate single time-jumping (Harry needs to be able to go back in time in order to save himself).

What you are saying is basically 'absence of visual is good for making a postulate' without deliberately not taking into account the other hints are dozens of things around it.