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[Eckhart Aurelius Hughes]

Please use this topic to discuss A Metaphysician Looks at the Everett Interpretation by John Hawthorne, which is chapter 4 of the July book of the month Many Worlds?: Everett, Quantum Theory, & Reality edited by Saunders, Barrett, Kent, Wallace. Please also use this topic to discuss the commentary that immediately follows chapter 5 as a reply, Physics before Metaphysics by James Ladyman. We are discussing this book chapter-by-chapter, including a discussion for the introduction and the two transcripts. Please do not post in this topic until you have read chapter 4 and the commentary of chapter 4.

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What do you think of this chapter? What do you think of Hawthorne's ideas and arguments? What do you think of Ladyman's commentary?

Hawthorne's essay seemed to me much shorter than the previous chapters, but I think concision and admitting one's own limitations in being able to contribute to a debate can be useful. Or bluntly, sometimes less is more. I think Hawthorne does a good job naming two hurdles that Everettians and MWI-supporters need to overcome to support their interpretation.

Overall I like Hawthorne's chapter, but I did not like the god analogy frequently used in the earlier part of the chapter. That's not to say that I don't agree with the point, but I just did not find the analogy appealing or clarifying as I think a good analogy would be.

Philosophically, I think Hawthorne does a great job addressing the issue of "metasemantical principles". I think his points on metasemantical principles provide a useful framework for countering the modal-dependent realism proposed by Hawking in the previous book of the month. I like that Hawthorne spells out some candidates:

To get to the flavor of things, here are some candidate metasemantical principles: (i) The causal theory of reference: in general singular terms refer to things that they're causally connected to, albeit sometimes by a long causal chain. (ii) David Lewis's proposal: other things being equal, predicates semantically gravitate to more natural properties rather than less natural properties rather than less natural properties. (iii) Timothy Williamson's principle of knowledge maximization: other things being equal, if we know more according to one semantic profile then according to another, that constitutively weights in favor of the former.

It seems to me that these candidates do not have to be mutually exclusive in that we can weigh different models or interpretations or "gap bridges" by a combination of all of those factors.

Anyway, what do you all think?

The Commentary by James Ladyman

What do you all think of the commentary by James Ladyman? I have to commend James Ladyman on being a good writer and an effective debater. He goes to town on Hawthorne's points, but in the way of an intelligent debater focusing on the points and charitably interpreting the other person's points.

Hawthorne's were more vague, though, and were admittedly too general. James Ladyman's response would have been more convincing if he was able to explain more why (he believes) either a single specific version of MWI or why MWI in general overcomes the alleged general hurdles/criticism ascribed by Hawthorne rather than just try to tear apart each of Hawthorne's points and respond to many ones with different examples from different MWI-supporters who each propose a slightly different version of MWI.

Also, I felt James Ladyman was very dismissive towards philosophy, but that does not make sense to me since most of his argument is a philosophical argument and indeed I think MWI -- as opposed to any other interpretation of QM or a sort interpretation-less QM such as perhaps the "instrumentalist" interpretation -- is in large part a philosophical theory. He makes a lot of interesting philosophical points that may be too numerous to each go into here in detail without being distracting from the main gist on the topic of QM. I would love to read more of James Ladyman's ideas on philosophy specifically and the various issues within contemporary philosophy and especially in regards to the philosophical points on which James Ladyman seems to disagree with the vast majority of philosophers.

In any case, I think the book was much better with James Ladyman's intelligent, focused article in it. Indeed, now with the back-and-forth I think this book is getting really exciting and engaging.

Anyway, what do you all think?