Wolfgang Schwarz

Hiatus

I'll be moving house tonight. In the new flat I don't have telephone/internet connection yet, so I might neither blog nor read emails for until I return from Bielefeld on Friday next week.

FOL 75, day 1

Things went not at all according to plan.

The biggest shock was that all presentations so far were fairly easy. Even Dan Willard's discussion of interesting theories in which interesting variants of Gödel's Second Incompleteness Theorem don't hold was easy for me to follow. I had expected the presentations to be like readings from a JSL volume.

The other surpising thing I noticed was how little most attendants know of what the others are doing. For example, when Hintikka talked about (surprise, surprise) the superiority of IF logic, the participants in the discussion seemed to know very little about it. (In this particular case that might be because those who know more about IF, like Hodges, have already given up arguing with Hintikka long ago.)

Conferences

In the next 10 days I'll be attending two philosophy conferences. The first, starting tomorrow and ending on Sunday, is the FOL75 logic conference here in Berlin. My plan for this is to sit quitely and nod or frown from time to time so that it doesn't show too much that I don't understand a word of what the speakers say. I'll also look at how some other people behave of whom I know that they also won't understand much. I guess for me this conference will be more like a field study in academic sociology.

The other conference, Monday through Friday next week, is the GAP5 conference at Bielefeld. I haven't really made up my mind on what I'll be doing there, but I hope to do some philosophy. If all goes wrong, I can still spend some time at the excellent library of Bielefeld university, catching up on the literature I'm missing in Berlin.

Spacetime and the Worldmate Relation

Lewis does not want to take the worldmate relation (that holds between two things iff they belong to the same world) as primitive. He proposes two alternatives. The first is that things belong to the same world iff they stand in ("analogously") spatiotemporal relations to each other. According to the second, more general, proposal things belong to the same world iff they stand in fundamental external relations to each other, whether or not these relatios are (analogously) spatiotemporal. I'm not sure if I fully understand the difference between these three alternatives. Here is why.

Scrambled Words

I think this only works with simple sentences containing short and familiar words. To test this, I wrote a little bookmarklet: scramble! If you bookmark this link (by using the context menu) and open it on any webpage, it will scramble the words on it. (If you click it, it will scramble the words on this page.) It should work in all browsers that support the W3C DOM, but I've only tested it in Mozilla.

[Update 2003-09-23]: I've updated the bookmarklet so that it doesn't count punctuation marks as parts of words any more.

[Another update 2003-09-23]: Sorry, there was a typo in the previous code.

Indistinguishable?

Re dense worlds, Dave Chalmers asks in what sense worlds that differ only in which intrinsic properties play which roles are indistinguishable. That's a very good question, and I'm afraid I don't have a good answer. He notes that those worlds differ in lots of respects, including their laws and quite probably the perceptions of their inhabitants.

What I want to say is that the worlds are somehow 'structurally alike', or 'isomorphic'. But that's hard to cash out. Is every Ramsey sentence that is true of one of them also true of the others? Then I would first have to restrict the 'old' terms of the Ramsey sentence. But that's a minor problem. What's worse is that this doesn't take care of more complicated rearrangements, where different parts of roles are played by different properties. Here the quantifiers of the Ramsey sentence would have to range over very gerrymandered (though intrinsic) properties. And given that gerrymandered properties are generally supposed to be causally inefficacious this is dubious. And finally, even if the Ramsey sentence account would work, I would still have to say why worlds that cannot be distinguished by Ramsey-sentences (or are otherwise 'structurally alike') are in any reasonable sense indistinguishable.

Shrugging off Sceptical Alternatives

Yesterday I said that Lewis might just shrug off arguments about other-wordly people who, despite being in the same evidential situation as we are and despite using the same kind of reasoning, get the laws of nature and the reference of their terms completely wrong: He could agree that such people are just as possible as similarly deluded people in counter-inductive worlds or even more deluded brains in vats.

But Lewis himself uses an argument of the same form against the non-indexical account of actuality (Pluarlity, p.93):

Readings on Quidditism

My attempts to get a copy of 'Ramseyan Humility' were unsuccessful, so I searched the web in the hope that somewhere somebody might have said something about what Lewis says in that paper. This is how I came across Paul Mainwood's BPhil Thesis Properties, Permutations and Physics (PDF). It's a very good thesis and contains (in section 4) an extended discussion of some of the problems I'm struggling with.

Humean Confusion

I'm confused. It seems to me that the Dense Worlds Argument refutes Lewis' Humean Supervenience thesis: Not all facts about worlds without alien properties are determined by the distribution of fundamental properties over space-time points. But that's not what really worries me.

What worries me is that I don't know what to blame. I don't see any move that doesn't lead into further difficulties. Consider blaming HS. If HS is false, then our world either contains extended things (as opposed to points) that instantiate fundamental properties, or it contains things that stand to each other in fundamental but not spatio-temporal relations. Let's focus on the second possibility. It is certainly conceivable that fundamental properties are instantiated by extended things. But does this help? Suppose all fundamental properties are instantiated by cubes with a volume of 1 nm^3 (or stages of such cubes with volume 1 ns*nm^3). Then the same kind of shuffling as in the dense worlds argument still shows that the interesting facts about our world are independent of the distribution of fundamental properties. But this time HS is not among the assumptoins, so we can't use the argument as a reductio against it.

Content, Context and the First Dimension -- Second Try

This is a rewrite of last week's posting, which I now find rather obscure. Basically, I'm trying to introduce A-intensions in a way different from the possibilities discussed in David Chalmers' "Foundations". The "contextual" approaches he discusses look like non-starters to me, and I don't like his own "epistemic" account, partly because of worries about his use of ideal language and partly because I would very much like to explain a priori knowledge with knowledge of A-intensions rather than the converse. Most importantly, I think there is something wrong with the very question he asks. Or at least there's something wrong with where the question is asked.