Mysterious Answers to Mysterious Questions
1) Great post and great comments.
2) Like a few people have mentioned, using a life force as an explanation isn't necessarily a bad thing. It depends what you have in mind. You could believe in the life force but not be breaking any of the four curiosity stoppers. It would be interesting to know how many people used life force as a curiosity stopper when it was popular. I would guess that most people did use it as a curiosity stopper. Sounds like a good job for those experimental philosophers to show they do more than just polls about intuitions.
3) "You have a little causal diagram in your head that says ["Elan vital!"] -> [hand moves]. But actually you know nothing you didn't know before. You don't know, say, whether your hand will generate heat or absorb heat, unless you have observed the fact already; if not, you won't be able to predict it in advance."
I disagree that you know nothing more than you did before. When I think of a life force I picture different things than, say, electrical force. Maybe your concept of life hasn't substantially changed, but it has been enriched slightly, and the more you enrich a concept the more falsifiable it becomes. I would argue that the more falsifiable a concept is, without being shown to be false, the more useful it is (in general). For instance, if I said meaning was holistic, I think this is somewhat analogous to saying motion in the living is generated by a life force. It loosely constrains other things you can believe about meaning or life.