tailcalled comments on Magic and the halting problem - Less Wrong

-5 Post author: kingmaker 23 August 2015 07:34PM

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Comment author: tailcalled 23 August 2015 08:21:23PM 4 points [-]

I personally subscribe to the Many Worlds Interpretation of quantum mechanics, so I effectively "believe" in the multiverse. That means it is possible that somewhere in the universal wavefunction, there is an Everett Branch in which magic is real.

Nope. The laws of physics are the same in all branches.

Or at least every time someone chants an incantation, by total coincidence, the desired effect occurs.

Those branches would be extremely rare.

Alan Turing pondered a related problem known as the halting problem, which asks if a general algorithm can distinguish between an algorithm that will finish or one that will run forever.

I don't find it very obvious how this is related.

So how would a person distinguish between pseudo-magic that will inevitably fail, and real magic that is the true laws of physics?

The pseudo-magic will with large probability fail the next time you test it.

And finally, what if our entire understanding of reality, including logic, is mere deception by happenstance, and everything we think we know is false?

Then you would find out very soon, unless you postulate something to keep the system stable.

Comment author: Houshalter 23 August 2015 11:29:22PM 0 points [-]

Nope. The laws of physics are the same in all branches.

The laws of physics are the same (in MWI, not other multiverse theories.) But there could be a universe where the are are advanced aliens with nanotech, which for some reason decide to mimic magic exactly. Or where, mysteriously, every time someone says "wingardium leviosa", objects happen to levitate, just by chance of random quantum effects.

I do think that both of these universes are so unlikely we shouldn't worry about ever being in them. But I think that is what OP is getting at.

Comment author: DanielLC 24 August 2015 07:04:58AM 0 points [-]

I think that the first universe is sufficiently more likely than the second that you shouldn't assume it's a coincidence, and you should expect wingardium leviosa to keep working.

Comment author: Houshalter 24 August 2015 09:37:01PM 0 points [-]

I agree, but I think OP is referring to the second situation. He's not saying that it's probable, just that it's possible and we can't ever rule it out. These issues go away when you internalize probability, but I understand how people can be confused on issues like this.

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