So I don't see any means to escape the conclusion that given mereological universalism, some things trivially move faster than light. Lots of things, in fact. Perhaps that's less troublesome than I thought because these things don't actually violate any physical laws.
For instance, I guess the principle that physics looks the same for all things that move with constant speed relative to each other has to be restricted to things with speed < c anyway. (At least Lorentz transformation doesn't make much sense if v = c.) If so, the exclusion of faster-than-light fusions from the principle is already built in and we don't need to worry about e.g. what such a fusion's proper time might be.
The Brock/Rosen objection against modal fictionalism goes as follows. The modal fictionalist holds that
1) Necessarily p iff according to the modal fiction, at all worlds, P*,
where P* is the modal realist's paraphrase of P, and the modal fiction is the modal realists' theory. But the modal realist holds that it is true at every world that there are many worlds. That is,
2) According to the modal fiction, at all worlds, there are many worlds.
It follows from (1) and (2) that
Let A and C be two distinct objects such that C exists at a later time and a
different place than A.
Let F be the mereological fusion of A and C. Question: Does F move from
the location of A to the location of C? I don't think so. If a thing moves
from one location to another, there should be a continuous path from the one location
to the other along which the thing moves.
So let B1, B2, ... be (continuum many) further objects (perhaps spacetime points, if nothing else is around)
that lie on a continuous spacetime path
between A and C, and let F be the fusion of A, B1, B2, ..., C. Does F now move? I'm not sure.
Maybe when a thing moves the later stages should depend causally on the earlier
stages. Or maybe the concept of movement is not applicable to gerrymandered fusions like F.
Do Escher's "impossible pictures" really show impossible situations? Andrew Lipson and Daniel Shiu have built Lego models of the waterfall, the infinitely ascending stairs, and the Relativity picture. And Sugihara Kokichi made some more impossible objects out of paper. (Via der Schockwellenreiter and the Cartoonist).
At first, I thought teaching students an informal semantics for predicate logic was only a compromise we had to choose because the real thing, formal model theory, is just too difficult for beginners. But now I'm inclined to believe that the informal semantics is itself the real thing. Maybe for those of us who have no quarrals with set theory, the difference is only superficial since both accounts assign the same truth conditions to all sentences, and truth conditions are all that matters. But that's not quite true. For example, when we talk about all sets (or all classes, or all things whatsoever), standard model theory is in trouble. I think it's silly to conclude that we can't really talk about all sets or classes or things. We obviously can do so in English, and we can also do so in (interpreted) first-order logic.
I've already mentioned that I moved into a new flat recently. This in itself isn't very remarkable as I'm used to moving house every couple of months. What's remarkable is that this time I've actually rented the flat. I still don't really know why I did that. It's a nice flat in Prenzlauer Berg (near Helmholtzplatz) with two rooms, a balkony, and Ofenheizung, but it's far too big for me and my two bags of personal belongings. So if you're visiting Berlin and need a cheap place to stay, drop me a line.
I've been running MacOS 8.6 for more than a year now. Since many programs I like aren't available on MacOS Classic at all (like any reasonable web server), or aren't updated any more (like Mozilla), I finally decided to make the switch, and I switched to Debian Linux. I've never used Debian before and I've never used Linux on a Mac, so I'm not sure what to blame. At any rate, I found the installation rather painful. It took me several days to set up the basic system with a working X server and a working dial-up connection. Then, last week, I tried to install a different kernel in order to get my ethernet card to work. The result is that now the system completely ignores my keyboard. Since I can't even login without the keyboard I don't know what to do next. Maybe I'll read some philosophy.
Luckily, I've put the new system on a new (well, second-hand) hard disk, so for now I'm back to MacOS 8.6.
Suppose we are relativists about moral judgements. That is, we believe that, for example,
"One should not engage in premarital sex"
may be truely asserted by somebody iff according to his moral code (or the moral code of his community, or something like that) one should not engage in premarital sex. The important part here is of course "truely". Noone denies that if you believe that one should not engage in premarital sex then if asked about it, you should say so. That's not relativism. Relativism as I understand it holds that what you said then would be true.
The GAP conference is over. There have been a couple of nice symposia on the a priori: George Bealer and David Papineau discussed the significance of a priori reasoning in philosophy, and Frank Jackson and Brian McLaughlin talked about a priori physicalism. I would like to comment on this, and also on some talks I heard about relativism and contextualism, but at the moment I'm a bit tired of philosophy, and my arms also aren't well. So I decided to do something useful for a change and went to Munich to save the rainforests. I'll be back in Berlin on Monday.
I'm in Bielefeld at the GAP5 conference. The overall quality of the talks so far hasn't been very good, but I'm told it's always like that at philosophy conferences.
One of the most tedious presentations was Manfred Kupffer's discussion of arguments for the claim that we don't know a priori whether Hesperus is Phosphorus. In contrast, it was much more enjoyable to listen to Karl-Georg Niebergall who suggested that all of mathematics is in fact about certain concrete lines (straight ones, triangles, rectangles, and circles, to be precise) infinitely many of which exist somewhere in our universe. The lesson is that arguing for an obvious truth is generally much worse than arguing for something absurd. (I asked Kupffer whether anybody ever denied what he is arguing for, and he said Scott Soames did. If that's true then Soames has learned that lesson.)