Nomic Facts and the Future
Suppose some thing x turns F, and a little later some other thing y turns G. x is the only F throughout history, so on a Humean account of laws of nature, it may well be just a coincidence that y's being G followed x's being F. Suppose it is.
But now consider another world just like this one except that in the far future, lots of G-turnings follow lots of F-turnings so that in this world, it is a law that whenever something turns F and another thing is suitably related, then that other thing turns G. In such a world, x's turning F caused y's turning G.
So if, in the original world, the future had been different in a certain way, then x's turning F would have caused y's turning G. In this way, it seems that nomic facts about the present counterfactually depend upon future events. That sounds bad, especially since so many common-place facts, including facts about intentional content, knowledge and reference, are nomic in the relevant sense because they somehow involve causation.
(This is not a case of backtracking, and probably not even of backwards causation: intrinsically, the present does not depend on the future. But on Humeanism, nomic truths do not supervene on the intrinsic nature of the past and present.)
Hello Wo.
Of course on any Humean account- in particular Lewis'- what laws there are depends on the pattern of exemplifications of properties (for Lewis- fundamental natural properties) throughout all space and time. This has consequences that are counter to intuitions (since our intuitions are partly shaped by non-Humean concepts) but this should not disturb someone who is convinced of Humeanism (say by objections to the idea of non-Humean laws governing events). As you observe worlds that match our world until now (in which only once an F was followed by a G) but which differ after now (say in having many Fs followed by Gs) may have different laws from our world. (The same point can be made about Fs followed by Gs in the past but in far away galaxies) Assuming that if Fs are followed by Gs is a law then Fs cause Gs (which you seem to be assuming but of course this is not Lewisâaccount of causation) then it seems to follow that if the future were very different (in their being events that make Fs are followed by Gs a law) then F would have been a cause of G. But why should this bother Lewis or you? One reason is if one mistakenly thought that this counterfactual entails that the future causes the laws. But it doesnât. It says that what laws there are metaphysically depends on the future (and the past) but not that the future causes what laws (and whether events are or are not causally related.) Further, if the laws of our world cover all events (a defeasible criterion for lawhood that Lewis should add to simplicity and informativeness) then the counter to fact future that renders many Fs are followed by Gs a law (on Lewisâ account of laws) is a counter legal future. One shouldnât be upset then that in a counterlegal world there are different causal relations. So it is right that on Lewisâ account what you know (refer to etc.) metaphysically depends on the future (and on events in far away galaxies) but this shouldnât trouble Lewis unless there is a non-question begging argument that this isnât so. John Hawthorne thought he had such an argument (I think it is in Nous) but it is not hard to see that there are good Humean responses (Brian Weatherson gives some in his blog a year or so ago).
Cheers,
Barry