After we came out of the church, we stood talking for some time together of Bishop Berkeley's ingenious sophistry to prove the non-existence of matter, and that every thing in the universe is merely ideal. I observed, that though we are satisfied his doctrine is not true, it is impossible to refute it. I never shall forget the alacrity with which Johnson answered, striking his foot with mighty force against a large stone, till he rebounded from it, 'I refute it thus.' -- Boswell's Life of Samuel Johnson
Sometimes, when discussing philosophy (or anything based on philosophy), the person you're talking with will defend their point by taking refuge under the shield of the undisprovable - that there's no way to prove the universe is real, or that you're real, or that there's any point in doing anything at all.
I've started using a shorthand argument against such positions, which I call the 'Stick Test'. I simply start (virtually) thwapping them repeatedly on the head with a stick, until such time as they can offer a reason for me to stop, with the minor caveat that the reasoning they give can't be self-annulling. For example, if their argument is that it is impossible to judge another culture's activities as being 'evil', I offer up the idea that it's part of my culture to repeatedly thwap people I disagree with on the head with a stick, and thus they have no justification for telling me to stop.
I've both had and inspired a few chuckles with this method... but I'm now throwing it in the fire - is it a *good* technique for pointing out that sort of flaw, or is it a poor tool which should be replaced by some *better* one? Assuming that it's not totally useless, what can be done to apply it most effectively?