Parallel Universes do not explain anything

Karl-Erik Eriksson compares The Many-Worlds Interpretation and postmodernism:

Sokal's definition of postmodernism is the following: an intellectual current characterized by the more-or-less explicit rejection of the rationalist tradition of the Enlightenment, by theoretical discourses disconnected from any empirical test, and by cognitive and cultThe Many-Worlds Interpretation and postmodernismural relativism that regards science as nothing more than a "narration", a "myth" or a social construction among many others.27

Let us make a description of MWI:

MWI is a world view that regards our experiences of reality as nothing more than one narrative about our world among innumerably many other narratives in a world of worlds. A narrative exists only in one world and cannot be communicated to another world.

This is probably close to what also an MWI proponent could accept.

Then what do postmodernists see in MWI? They see MWI as a world view structured in a way that is similar to postmodernism and therefore useful to support it. Even if postmodernists do not value science, they can value the prestige of science, as shown by Sokal [18]. Therefore, MWI can be felt as a scientific support for postmodernism.

He also cites Brian Greene's arguments for many-worlds:

Stage one — the evolution of wavefunctions according to Schrödinger's equation — is mathematically rigorous, totally unambiguous, and fully accepted by the physics community. Stage two — the collapse of a wavefunction upon measurement — is, to the contrary, something that during the last eight decades has, at best, kept physics mildly bemused, and at worst, posed problems, puzzles and potential paradoxes that have devoured careers. The difficulty [...] is that according to Schrödinger's equation wave functions do not collapse. Wavefunction collapse is an add-on. It was introduced after Schrödinger discovered his equation, in an attempt to account for what experimenters actually see. [[9], p. 201.]

No, the evolution of the wave function is not stage one. The wave function is not directly observable, so we can only infer estimated wave function by other methods.

This might seem like a minor point, except that Greene is going to argue that the Schroedinger equation is all we need. That cannot be.

John Preskill, in his recent podcast, also said that maybe unitary evolution of the wavefunction is all there is. But that cannot be all there is, because we still need an explanation for why we see discrete measurements.

Note the attempt to denigrate wavefunction collapse as an invention "to account for what experimenters actually see."! Yes, physical theories try to account for what experimenters see. They see collapse. Any theory not explaining collapse is not doing the job.

The many-worlds fans say that the collapse is seen as the splitting of the universes. So they have to have collapse as part of the theory, but they say the splitting is a mystery and cannot tell us much more than that.

[Each] of the potential outcomes embodied in the wavefunction still vies for realization. And so we are still wondering how one outcome "wins" and where the many other possibilities "go" when that actually happens. When a coin is tossed, [...] you can, in principle, predict whether it will land heads or tails. On closer inspection, then, precisely one outcome is determined by the details you initially overlooked. The same cannot be said in quantum physics. [...]

There is not really any conceptual difference here.

The coin toss cannot be predicted with certainty. Maybe some overlooked details would enable a better prediction, but that could be true of quantum mechanics too, for all we know.

Much in the spirit of Bohr, some physicists believe that searching for such an explanation of how a single, definite outcome arises is misguided. These physicists argue that quantum mechanics, with its updating to include decoherence, is a sharply formulated theory whose predictions account for the behavior of laboratory measuring devices. And according to this view, that is the goal of science. To seek an explanation of what's really going on, to strive for an understanding of how a particular outcome came to be, to hunt for a level of reality beyond detector readings and computer printouts betrays an unreasonable intellectual greediness.

Many others, including me, have a different perspective. Explaining data is what science is about. But many physicists believe that science is also about embracing the theories data confirms and going further by using them to get maximal insight into the nature of reality. [[9], pp 212-213.

I am all for explaining data also, but just saying that anything can happen in parallel universes explains nothing.