In recent years there seems to have been a growing discussion surrounding MWI's ontology. In the 2010 volume "Many Worlds?", Simon Saunders has a chapter dedicated to discussing whether the worlds in MWI branch or diverge.

The branching view states that before a measurement there is 1 observer in 1 world, after the measurement there is 2 observers in 2 worlds. The divergent view states that there were 2 observers and worlds all along, but they were identical up to the point of differentiation, so there were no way for you to tell which world you were really in.

Alastair Wilson has written several papers on this in the last years: http://alastairwilson.org/

Any MWI proponents got any opinion either way?

  • $\begingroup$ Well, at least the observer before the observation was twice "thicker" in the sense his probability was twice greater and as such, his energy was twice greater (as energy of a wave function branch and everything in it is proportional to its probability). $\endgroup$ – Anixx Aug 15 '19 at 22:12
  • $\begingroup$ Since the question is closed for answers, I shall comment that this is one of the most interesting questions about MWI and has a clear answer (the worlds branch, not diverge). Deutsch proposed, in the 1980s, that worlds diverge because it wasn't clear how to assign probabilities to worlds. So he imagined the worlds already split and applied an extra ad hoc measure to them. Nowadays MWI theorists are happier about deriving the Born Rule from scratch and so have returned to the earlier,.more Evererttarian picture, of worlds splitting at each quantum event. $\endgroup$ – Michael C Price Oct 24 '19 at 10:00

The two interpretations only differ in ontology. Neither is bullshit, rather both are standard MWI. When you have an observer, this is a computational entity, and to map it to a wavefunction is a nontrivial task. Whether you decide to say there were "really" two observers that were exactly the same before the measurement or whether there was "really" only one observer which branched is a meaningless question in the sense of Carnap, and has no answer, not even philosophically.

The important principle is that the "number" of consciousnesses is determined by interaction with other entities. If you have a computer running a simulation of a conscious observer, and you decide to do a double-check step on each computational step, do you get a second observer? If you do the double-checking in a different computer, is it a new observer? Observationally, you only get a new observer when you talk to two different people, and this only happens after the two computations are distinct.

This question is entirely about philosophy of mind, and this is where computational and positivist formulation is most important.

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    $\begingroup$ I'll just rehash my earlier comment that copying a comment discussion verbatim into an answer is a really bad idea. It doesn't improve the usefulness of the answer because people aren't going to read it through. $\endgroup$ – David Z May 8 '12 at 6:19
  • $\begingroup$ @DavidZaslavsky: If people don't read it, it does no harm. In this case, I know people who care about this philosophy business will read it, because these are pedestrian anti-positivism arguments they hear from others. A positivist will not read it, but that's just saying that someone who already knows the answer will not read an answer. So I disagree. $\endgroup$ – Ron Maimon May 8 '12 at 14:41
  • $\begingroup$ Actually it does do harm, in that it makes people sort through a lot more information than they need to in order to make sense of the answer. Yes, there may be interesting arguments in the comments, but they should be summarized and organized, not copied verbatim. This conclusion is based on years of experience (not just mine) across the Stack Exchange network and other forums. And in any case, it's a network-wide policy that verbatim copying and pasting of comments is inappropriate - in fact, it's one of the core principles of Stack Exchange. As an official policy, this is not up for debate. $\endgroup$ – David Z May 8 '12 at 15:25
  • $\begingroup$ @DavidZaslavsky: I am debating it, I will never agree to it, it's ridiculous in this case. One must'nt give a rat's ass about votes and policy, or community standards. One must butt heads against these types of things, as they restrict usefulness. This type of discussion is the only way to clearly and briefly explain a philosophical point, as oppose to technical points, since people come in with completely incompatible points of view, and this shows up as a list of "but why this? and why that?". I'm surprised you are using policy and guidelines. $\endgroup$ – Ron Maimon May 8 '12 at 15:28
  • $\begingroup$ Well, I suppose I can take that as an indication that you're not going to summarize and organize the comments here ;-) If you don't like this particular policy, that's fine, but it doesn't change the fact that these sorts of contributions are inappropriate here. They would probably be better received on a traditional forum, so perhaps you could seek out an alternate venue for when you want to have extended discussions that will be permanently preserved. $\endgroup$ – David Z May 8 '12 at 15:31

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