This article should really be called "Patching the argumentative flaw in the Sequences created by the Quantum Physics Sequence".
There's only one big thing wrong with that Sequence: the central factual claim is wrong. I don't mean the claim that the Many Worlds interpretation is correct; I mean the claim that the Many Worlds interpretation is obviously correct. I don't agree with the ontological claim either, but I especially don't agree with the epistemological claim. It's a strawman which reduces the quantum debate to Everett versus Bohr - well, it's not really Bohr, since Bohr didn't believe wavefunctions were physical entities. Everett versus Collapse, then.
I've complained about this from the beginning, simply because I've also studied the topic and profoundly disagree with Eliezer's assessment. What I would like to see discussed on this occasion is not the physics, but rather how to patch the arguments in the Sequences that depend on this wrong sub-argument. To my eyes, this is a highly visible flaw, but it's not a deep one. It's a detail, a bug. Surely it affects nothing of substance.
However, before I proceed, I'd better back up my criticism. So: consider the existence of single-world retrocausal interpretations of quantum mechanics, such as John Cramer's transactional interpretation, which is descended from Wheeler-Feynman absorber theory. There are no superpositions, only causal chains running forward in time and backward in time. The calculus of complex-valued probability amplitudes is supposed to arise from this.
The existence of the retrocausal tradition already shows that the debate has been represented incorrectly; it should at least be Everett versus Bohr versus Cramer. I would also argue that when you look at the details, many-worlds has no discernible edge over single-world retrocausality:
- Relativity isn't an issue for the transactional interpretation: causality forwards and causality backwards are both local, it's the existence of loops in time which create the appearance of nonlocality.
- Retrocausal interpretations don't have an exact derivation of the Born rule, but neither does many-worlds.
- Many-worlds finds hope of such a derivation in a property of the quantum formalism: the resemblance of density matrix entries to probabilities. But single-world retrocausality finds such hope too: the Born probabilities can be obtained from the product of ψ with ψ*, its complex conjugate, and ψ* is the time reverse of ψ.
- Loops in time just fundamentally bug some people, but splitting worlds have the same effect on others.
I am not especially an advocate of retrocausal interpretations. They are among the possibilities; they deserve consideration and they get it. Retrocausality may or may not be an element of the real explanation of why quantum mechanics works. Progress towards the discovery of the truth requires exploration on many fronts, that's happening, we'll get there eventually. I have focused on retrocausal interpretations here just because they offer the clearest evidence that the big picture offered by the Sequence is wrong.
It's hopeless to suggest rewriting the Sequence, I don't think that would be a good use of anyone's time. But what I would like to have, is a clear idea of the role that "the winner is ... Many Worlds!" plays in the overall flow of argument, in the great meta-sequence that is Less Wrong's foundational text; and I would also like to have a clear idea of how to patch the argument, so that it routes around this flaw.
In the wiki, it states that "Cleaning up the old confusion about QM is used to introduce basic issues in rationality (such as the technical version of Occam's Razor), epistemology, reductionism, naturalism, and philosophy of science." So there we have it - a synopsis of the function that this Sequence is supposed to perform. Perhaps we need a working group that will identify each of the individual arguments, and come up with a substitute for each one.
One of those questions is not like the others, but I'd also like to hear an answer to all the others. Obviously, if even one answer is "Yes", then I will instantly toss it out the window unless it has an experimental consequence different from MWI or a strictly endogenous answer to the Born rule. ("We use the Born rule to decide which world survives!" is not endogenous, it is pasting an arbitrary mechanism attached to the same rule-of-unknown-origin treated as fiat.) If there are two "Yes" answers that aren't the same "Yes", I will toss it even if it has endogenous Born. Any damn idiot can introduce a bunch of magic and sneak in some fairly arbitrary linkage to measure which eventually yields the Born probabilities - I'd expect thousands of theories like that, and I'd expect none of them to be right. The great achievement would be getting Born without magic, where 'magic' is represented by a "Yes" to any of the above questions.
The framework of Wheeler-Feynman theory is just classical Maxwell electrodynamics with waves that converge on a charged particle as well as waves that spread from a charged particle. So it ought to be just as relativistic and local and deterministic as it usually is, except that now you're interested in solutions that have two oppositely directed arrows of time, rather than just one. (Remember that the equations themselves are time-symmetric, so "emission" of radiation can, in principle, run in either direction.)
In practice, they artificially ha... (read more)