Skeptizismus lebt!

Theorien wie der Kontextualismus (hier Willascheks Zusammenfassung für das Kontextualismus-Sonderheft der Deutschen Zeitschrift für Philosophie) gehen mit der skeptischen Herausforderung um, indem sie ihr einen Sonderstatus zuweisen. Das klappt umso besser, je weiter weg von der Alltagserfahrung sich die skeptische Frage positioniert, als Dämon oder Gehirn im Tank etwa. Umso interessanter muss daher ein Skeptizismus erscheinen, der das schlichte Ausweichen nicht zulässt. Bryan Frances zeigt in Scepticism comes alive (Oxford : Clarendon, 2005), wie das aussehen könnte. Das skeptische Argument, in der Fassung seines Vorworts:

In order to know P, one must be able to rule out some nonP possibilities. For instance, in order to know that the tree is a fir, one has to rule out the possibility that it's a spruce or a hemlock. At least, one has to rule out those possibilities provided they are real, scientifically respectable, 'live' hypotheses; one is aware that they have such respect; and one si perfectly aware that those hypotheses conflict with one's belief that the tree is a fir. For instance, you came across the tree while taking a stroll through a forest with a tree expert. You said the tree was a fir, but she said that it's quite hard to tell from this vantage-point because spruces and hemlocks look the same and there are lots of them around here. Those nonP possibilities are 'relevant alternatives', as it is often said. Perhaps the brain-in-a-vat possibility doesn't need to be ruled out; but the spruce and hemlock possibilities do need to be ruled out. Assuming I can't rule out the spruce possibility, I don't know that the tree is a fir -- even if the tree is a fir. At least, I don't know it's a fir tree once I'm aware of the live status of the spruce and hemlock possibilities.
But now here's the kicker: there are several real, scientifically respectable, 'live' hypotheses that can be used in the very same argument template as in the previous paragraph.

Was für Hypothesen könnten das sein? Hier eine Online-Zusammenfassung als Nous-Artikel aus Frances' eigener Feder.