Friends Don’t Let Friends Learn Physics From Yudkowsky

With the demise of Reddit, we have lost /r/SneerClub, the Internet’s hot spot for mocking those who proclaim allegiance to capital-R Rationality and related ideologies like longtermism. Somewhere in between the discussions of heavy stuff like sexual harassment in Effective Altruism culture and total frivolity were the rambles about science. I thought I would pull a couple such comments out of the archives and edit them into something shaped like a blog post. So, consider this your Attention Conservation Notice: if you’d rather not work through a self-admittedly rough explanation of how Eliezer Yudkowsky’s claims about quantum physics are just silly, exit now.

Yudkowsky clearly intends to argue that the scientific community is broken and his brand of Rationalism(TM) is superior, but what he’s actually done is take all the weaknesses that physicists have when discussing quantum foundations and present them in a more concentrated form. There’s the accepting whatever mathematical formulation you learn first as the ultimate truth, the reliance upon oversimplified labels and third-hand accounts rather than studying what the pioneers themselves wrote, the general unwillingness to get out of the armchair and go even so far as the library…

Let’s open with Yudkowsky’s “If Many Worlds Had Come First“, where a fake version of Hugh Everett trades places with a fake version of Niels Bohr. Now, to me this sounds like a bizarrely overcomplicated rhetorical exercise, but if it is to be done correctly, then the fictional Bohr should espouse the view of the historical Everett and vice versa. But because it’s showboating, that’s not what we get.

First, we get some bizarre revisionism:

Macroscopic decoherence, a.k.a. many-worlds, was first proposed in a 1957 paper by Hugh Everett III.

No, decoherence was introduced by Zeh in 1970. And it took another decade for the idea to take off, thanks to Zurek coming along with work that was (a) fairly interpretation-neutral in its presentation and (b) originally inspired by trying to clarify Bohr rather than dethrone him. Nowadays, the theory of decoherence is recognized as a calculational tool that anybody can use regardless of their preferred interpretation of quantum physics, because it’s just applying the standard math to a particular class of situations, and all interpretations agree on the standard math. Using “macroscopic decoherence” as a synonym for “many-worlds interpretation” makes no logical sense.

Then, we get a transparent attempt to make Everett look good while academia looks bad:

Crushed, Everett left academic physics, invented the general use of Lagrange multipliers in optimization problems, and became a multimillionaire.

The whole point of Lagrange multipliers was always “optimization problems” (minimizing or maximizing a functional in the calculus of variations is optimization); this should be “operations research” or “management science”. More fundamentally, though, one could with equal justice say that Everett lacked the temperament to argue for his ideas, antagonized and scorned those who most closely agreed with him, and died miserable. See what I did there?

It wasn’t until 1970, when Bryce DeWitt (who coined the term “many-worlds”) wrote an article for Physics Today, that the general field was first informed of Everett’s ideas.

False. Everett’s paper was discussed at the Chapel Hill conference in 1957, where Feynman came down pretty harsh on it. And in 1959, Everett met with more people than just Bohr when he visited Copenhagen. In 1962, Everett presented his interpretation at a conference at the Xavier University of Cincinnati, with prominent physicists like Wigner in attendance. And of course, all this is in addition to the fact that Everett’s ’57 paper was published in the Reviews of Modern Physics, one of the most prominent journals of the physics profession. Why didn’t more people care until the ’70s? (shrug) It answered no specific question about a concrete physics problem, and as noted above, quite possibly Everett himself was just not the man to sell it. My own impression of that paper was that it had enough places where it just assumed the math works out that it needed at least one more round of revision (to be clear about the problems, if not to solve them, since nobody has done that yet). But I too am judging it with the benefit of hindsight.

And suppose that no one had proposed collapse theories until 1957.

Bohr did not propose a collapse theory.

Now, I actually stumbled across “If Many Worlds Had Come First” tonight while looking for something else, Yudkowsky’s “explanation” of Bell’s theorem. It’s a muddle of percentages that make my eyes glaze over, and quantum information theory is my job. Why he does it that way, I have no idea. Bell’s original argument from 1964 is actually easier to follow, and Yudkowsky name-drops the GHZ state, so he seems to be aware of more recent developments that made the point even simpler. Perhaps he wanted to make the mathematics “elementary”, but by not using (Mermin’s improvement of) the GHZ argument, he brings in needless trig functions and introduces a whole heap of angles that look completely arbitrary. It’s a mess.

What does Bell’s Theorem plus its experimental verification tell us, exactly?

My favorite phrasing is one I encountered in D. M. Appleby: “Quantum mechanics is inconsistent with the classical assumption that a measurement tells us about a property previously possessed by the system.”

OK. Let’s dig in. That paper isn’t about Bell’s theorem; it’s about the Bell–Kochen–Specker theorem, another result in the same area also proved by Bell (and independently by the team of Kochen and Specker). It has a similar upshot, but its assumptions are more abstract and harder to justify physically.

But it gets better. In his very next paper, Appleby writes,

If I am asked to accept Bohr as the authoritative voice of final truth, then I cannot assent. But if his writings are approached in a more flexible spirit, as a source of insights which are not the less seminal for being obscure, they suggest some interesting questions. I do not know if this line of thought will be fruitful. But I feel it is worth pursuing.

Not quite the message that Yudkowsky would want to convey. But it was there for him to read, written in 2004, years before LessWrong even existed.

I’ll admit, I probably wouldn’t have noticed that or gone on at length about it, were it not for the fact that Appleby is a collaborator of mine.