Sometimes I wish I hadn't done something, and that I could undo what I did. That is a coherent desire. What I desire is after all not that the world be such that at time t1, I do X, and then at t2, I do something else to the effect that at t1, I didn't do X. That's nonsense (unless I wish to inhabit a branching universe, which, let's stipulate, I don't). Rather, I desire that at t2, I do something to the effect that at t1, I didn't do X in the first place.
A harder case: suppose I wish I had never existed, and wish to undo my existence. That still makes sense, I guess. It's like the wish to be somebody else: I wish to do be a person who does something such that by doing this, they make it the case that the person I in fact am never came into existence.
Does the conceivability of zombies threaten type-A materialism, the claim that all mental truths are a priori entailed by the physical truths?
We can imagine beings exactly like us in all physical respects, but lacking consciousness. But this doesn't threaten type-A materialism (as I mentioned here). After all, it isn't a priori that materialism is true. It could have turned out that ectoplasmic states, rather than brain states, occupy the causal roles that, by analytic necessity, belong to mental states. Suppose it turned out that way. Then duplicating only our physical constitution would result in a being that is physically just like us, but lacking consciousness. So by type-A materialist lights, it is conceivable that things are such that there are beings physically just like us without consciousness.
Is it metaphysically necessary that like charges repel? One might think so: one might think that "charge" is partly defined by its theoretical role, so that this claim comes out analytic. Or one might think that science reveals to us the essence of properties, and that it is part of this essence of charge that like charges repel.
If that law about charges is metaphysically necessary, one might suspect that quite generally, nomological necessity coincides with metaphysical necessity (though see below for an argument against this suspicion):
Sorry, the server has been down quite a lot recently. Hope it's back to normal now.
Here's the talk I gave at Kioloa. It's partly identical to the talk I gave at GAP.6 in Berlin, but with more speculative ideas towards the end and less missionary appeals in between.
Are all truths entailed by logical truths? Depends on what we mean by "all truths" and "entailed" and "logical".
Let's understand a truth to be a true sentence of English, possibly enriched by logical vocabulary. As for entailment, let's distinguish metaphysical entailment (necessarily, if P then Q) from analytical (or conceptual or a priori) entailment. The precise definition of these notions, and the differences between them, won't matter.
I was at a student conference at the ANU Coastal Campus in Kioloa this weekend. Australia doesn't have a proper railway system, so I went there by bike. I didn't really know what to expect, since the maps here are about as bad as the railway system. Here's a brief description of the route.
On the way down, I went via Captain's Flat to Braidwood and from there on King's Highway and Princess Highway to Kioloa. With a few short sightseeing detours, that's about 230km. The way back I stayed on King's Highway after Braidwood, bringing the total distance to 210km.
The route profile is similar on both ways: about 30km up- and downhill after Canberra, then 20 km almost flat, then it goes mostly up for ~10 km to the Great Dividing Range/Tallaganda NP (the highest point of the journey), then down again, and then mostly flat, before the road steeply descends into the coastal area. Then it's a lot of uphill and downhill again to Bateman's Bay (35km), and then another 45km slightly hilly to Kioloa beach. In total, I'd estimate you go about 1300m down and 800m up from Canberra to Kioloa. The detour to Captain's Flat is definitely worth it for the nice views and the almost car-free roads, but it's also more demanding, not only because it's longer, but also because the road is partly unsealed. Even on the Highway, there isn't that much traffic though, especially between Bungendore and Bateman's Bay. With good breaks and lights, lots of water and a break during the hottest time of the day (which I took on the way down, but stupidly not on the way back), this is a very enjoyable journey.
JC lent me his camera, so I took a lot of boring pictures of landscapes and dead animals.
So I was given a replacement computer now until the other one arrives. If you're waiting for a sign of life from me, I'll probably contact you soon.
But first some philosophy. I want to argue that necessitarianism is compatible with Humean recombinatorialism because powers aren't intrinsic in the sense relevant to this. I also want to suggest that in an ontology of powers, what's fundamental aren't really the powers, but the causal or nomic relations.
Necessitarianism is the view that properties like mass and spin have their causal or nomic role essentially: if a property doesn't behave like mass, it isn't mass. It follows that the laws about mass are metaphysically necessary. (There are many different views in the vicinity here, maybe more about this later.)
I've just arrived in Canberra, where I'm visiting the ANU for a little while.
To be an electron is to roughly satisfy our electron theory;
to be a banana is to roughly satisfy our banana theory. To say
that electrons or bananas are such-and-such is equivalent to saying
that things (roughly) satisfying a certain theoretical role are
such-and-such.
Thus our Total Theory of the world is arguably a priori equivalent
to its "electron" ramsification or its "banana" ramsification, in
which all occurrences of "electron" and "banana", respectively, have
been replaced by existentially bound variables. What Total Theory adds
to those Ramsey sentences is only the Carnap sentence for "electron"
and "banana": the material conditional with the Ramsey sentence in the
antecedent and Total Theory in the consequent. And this conditional is
arguably analytic.
Lots of interesting stuff came up at the Summer School and the GAP and the A Priori workshop. Here's just two quick notes on something Jason Stanley mentioned in his talk on "Knowledge and Certainty".
Jason argued that knowledge does not entail certainty. He pointed out that in Unger's arguments to the opposite conclusion, "know" is always emphasized, as in:
Oh dear, I just came back from the summer school with David Chalmers in Cologne, and it looks like some mysterious event has yesterday reset my server to August 30. This means that if you've sent me an email during the last 6 days, it hasn't reached me: please re-send. Any weblog comments from this time are also lost (I've recovered the earlier ones from my feed reader.), and the same goes for the new anti-comment spam system I set up before I left and, ironically, the backup system I had only half finished.