A Short Argument: Modal, Schmodal!
Since other possible worlds are spatio-temporally distinct from our own, how things are at another possible world can have no causal influence on our own. Since how things are at another possible world can have no causal influence on our own world, our world would be the way it is no matter how things were at other possible worlds. So our world is the way it is, no matter how things are at other possible worlds.
Obviously something funny is going on here and it probably has something to do with ways our world is. For example, the modal facts -- which sure seem to be ways our world is -- would change with many alterations in how things are at other possible worlds. And a lot of philosophical ink has been spilled in showing how facts that don't seem to be modal facts really are modal -- e.g. causal facts, facts about knowledge, perception and the like. How things are with other possibilities matters more than Grandma might have supposed. So we have reason to believe the argument is unsound.
...and yet...
Imagine, however, that God has the power to change what is possible -- perhaps only for restricted forms of possibility. Suppose, then, that every 10 seconds he institutes changes in the local modal neighborhood such that what is now nomologically possible becomes nomologically impossible. Yet He leaves our world intrinsically untouched. Lots of things would be in flux: the laws of nature (by definition), the causal facts (what causes one thing in one 10 second span will cease to exert causal influence the next), the "epistemic" facts (we'll shift from knowing/perceiving many things to not).
On the other hand, from our perspective (I strongly intuit), nothing will shift. Since these changes are changes that exert no causal influence on us, it will seem as if the world remains unchanged. So part of what remains the same would be our consciousness. But, the sameness is not just phenomenal: similar events still follow one another as before. Even if Xs no longer cause Ys (because the modal facts have shifted), there would seem to be something like causation. Xs still follow Ys -- Xs HUMECAUSE Ys, you might say.
What is preserved if the modal facts are allowed to vary willy-nilly? And anyway, how could the modal facts matter?!
It is also epistemically possible that the imagined scenario is not genuinely possible... it certainly seems to put the Lewis-machinery through the wringer to imagine the space of possible worlds itself being reconfigured. Anyway, you might affirm the following exciting thesis: Modal facts supervene on actual facts, in which case the imagined scenario is impossible.
A technical (and probably totally opaque) note: Since the local modal neighborhood is defined by similarity, God would have to change the accessibility relation while he's at it... or something. But no doubt God could pull it off, whatever is required.
Obviously something funny is going on here and it probably has something to do with ways our world is. For example, the modal facts -- which sure seem to be ways our world is -- would change with many alterations in how things are at other possible worlds. And a lot of philosophical ink has been spilled in showing how facts that don't seem to be modal facts really are modal -- e.g. causal facts, facts about knowledge, perception and the like. How things are with other possibilities matters more than Grandma might have supposed. So we have reason to believe the argument is unsound.
...and yet...
Imagine, however, that God has the power to change what is possible -- perhaps only for restricted forms of possibility. Suppose, then, that every 10 seconds he institutes changes in the local modal neighborhood such that what is now nomologically possible becomes nomologically impossible. Yet He leaves our world intrinsically untouched. Lots of things would be in flux: the laws of nature (by definition), the causal facts (what causes one thing in one 10 second span will cease to exert causal influence the next), the "epistemic" facts (we'll shift from knowing/perceiving many things to not).
On the other hand, from our perspective (I strongly intuit), nothing will shift. Since these changes are changes that exert no causal influence on us, it will seem as if the world remains unchanged. So part of what remains the same would be our consciousness. But, the sameness is not just phenomenal: similar events still follow one another as before. Even if Xs no longer cause Ys (because the modal facts have shifted), there would seem to be something like causation. Xs still follow Ys -- Xs HUMECAUSE Ys, you might say.
What is preserved if the modal facts are allowed to vary willy-nilly? And anyway, how could the modal facts matter?!
It is also epistemically possible that the imagined scenario is not genuinely possible... it certainly seems to put the Lewis-machinery through the wringer to imagine the space of possible worlds itself being reconfigured. Anyway, you might affirm the following exciting thesis: Modal facts supervene on actual facts, in which case the imagined scenario is impossible.
A technical (and probably totally opaque) note: Since the local modal neighborhood is defined by similarity, God would have to change the accessibility relation while he's at it... or something. But no doubt God could pull it off, whatever is required.
posted by Idris at 1:00 PM
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