I've been reading Dan Dennett's 'A route to intelligence: oversimplify and self-monitor', in which he discusses the queer idea of "changing the course of history":
How could you change the course of history? From what to what? If history is simply the sequence of events that actually occur, then of course you can't change history. People say you can't change the past, and that's true enough, but then you can't change the future either...
[O]ne has to be thinking of an anticipated history, the way history is going to go ceteris paribus, the way history is going to go unless someone does something, or until someone does something, or in spite of what someone does. These verbs of agency can have no foothold outside the framework of a projected, aniticpated history, even when they are used to characterize the effects brought about by entirely inanimate objects.
He goes on to describe a scenario whereby a meteor is heading towards the earth, and we're all frantic until an unnoticed second meteor deflects the first one, "narrowly averting the catastrophe, preventing calamity." However, given full information, we could have seen that "there was never going to be a catastrophe. It was merely an anticipated catastrophe -- a mis-anticipated catastrophe." Dennett thus suggests that the sense in which the meteor was 'set' to hit earth is merely epistemic, rather than reflecting any natural disposition or 'default outcome' in the world, from which we were narrowly saved.
I'm not sure that's the full answer, though. There seems a sense in which the meteor really was, quite literally, 'on course' to hit the earth. It was 'deflected', which is precisely to say that its course was changed. This may be reflected in the modal fact (if it is one) that in most close possible worlds, the catastrophe indeed occurs. It's an open question whether this modal fact actually holds of the scenario, however. It might if small changes to the course of the second meteor would cause it to miss the first, while equivalent changes to the first meteor would not have caused it to miss earth. Otherwise - if the course of catastrophe was not modally robust in the first place - my modal account implies that the meteor was not really 'set' to hit the earth in any objective sense at all.
Let's see how this modal account applies to the puzzle discussed in my old post on framing thought experiments:
Weatherson notes that "where we set the 'zero-point' or status quo makes a big difference for how we act." But is there really any fact of the matter about what the 'default' outcome is? Kahneman and Tversky's classic example seems to suggest that this is merely a difference in our descriptions, not in reality. Whether you say that 400/600 will die, or that 200/600 will be saved, you describe one and the same fact. But the descriptions differ in their implied baseline, or what they convey as being "the natural progression of things". Could there be a metaphysical fact of the matter regarding where the true baseline lies? What sort of fact could this be, that would tell us whether a survivor was saved from the jaws of death, or whether it was simply a matter of death failing to cut his life tragically short? When faced with branching possibilities, how can we say that one is the "default" path of fate, and the other some kind of unnatural "diversion"? (But if we can't do this, then what is our basis for caring more about "losses" than "forfeited gains"? Doesn't this distinction require a baseline?)
My new suggestion is that the modal facts can provide such a baseline. The baseline is whichever event (dying or being saved) occurs in most close possible worlds. If you are overwhelmingly likely to obtain some benefit, then failure to obtain it in the actual world is properly classified as a loss, and not merely a forfeited gain.
Eh, so much for deflationism. It turns out I'm a "realist" about baselines too! A somewhat revisionary one, though. This certainly doesn't match our common understanding of the doing/allowing distinction, and nor would I expect it to have such (or, perhaps, any) normative significance. What do you think?