Shrugging off Sceptical Alternatives
Yesterday I said that Lewis might just shrug off arguments about other-wordly people who, despite being in the same evidential situation as we are and despite using the same kind of reasoning, get the laws of nature and the reference of their terms completely wrong: He could agree that such people are just as possible as similarly deluded people in counter-inductive worlds or even more deluded brains in vats.
But Lewis himself uses an argument of the same form against the non-indexical account of actuality (Pluarlity, p.93):
What a remarkable bit of luck for us if the very world we are part of is the one that is absolutely actual! Out of all the people there are in all the worlds, the great majority are doomed to live in worlds that lack absolute actuality, but we are the select few. What reason could we ever have to think it was so? How could we ever know?
Couldn't a proponent of absolute actuality shrug off this argument, too? I don't think so. There is an important difference between those cases. In the cases mentioned above, accepting the relevant possibilities (where our counterparts are deluded) just means accepting that a methodologically ideal theory might nevertheless be false, and that even the best inductive argument does not necessarily preserve truth. That doesn't sound too implausible. It is different with the case of absolute actuality: Here it seems intuitively that we do have an a priori guarantee that our world is the actual one. We are absolutely certain about this. That is, we deny the existence of any alternative possibilities.