Slow switching is something that has always kind of bothered me and below I pose a problem for fans of slow switching. Slow switching is this thing that happens in a bunch of thought experiments in the philosophy of mind. For example:
By “water” you mean water. But one day you go to Twin Earth, where the stuff that seems just like water and is called “water” isn’t water at all. It is twater. By the way, you were transported to Twin Earth unawares, so your initial attempts to think and utter truths about that twater stuff are doomed to fail since you are really thinking about water. However, through the miracle of SLOW SWITCHING, after a while (days? weeks? years? Nobody knows) your attempts to think and utter truths about that twater stuff now succeed. By “water” you now mean twater and all of this was achieved without any differences except those involved in the mere passage of time. Thus, slow switching happens without you noticing: it makes no subjective impact on you or anyone else.
But here’s a little puzzle that I’d like to pose for people who think this slow switching stuff is supported by intuition. Consider two Twin Earth scenarios like the one above wherein scenario A is just like the one above and scenario B differs with respect to the following demonic intervention. In scenario B, after each second of subjective time experienced on Twin Earth B, the demon freezes all activity on Twin Earth B for 99 objective seconds. The net result is that processes that subjectively take the same amount of time on A and B, take a hundred times longer objectively to complete on B.
Here’s the puzzle. Suppose that slow switching takes a year on Twinearth A. On Twinearth A, objective and subjective years are equal. However, on Twin Earth B, a subjective year takes a hundred objective years to get through. How long will slow switching take on Twin Earth B? My bet is that people that have the slow switching intuition will want to say that it takes 100 objective years. This would show, though, that the slow switching intuition requires a subjective supervenience base. But this seems in tension with the part of the intuition that says that slow switching can take place without anyone noticing, that it is the objective facts upon which slow switching supervenes (facts about e.g. H2O and XYZ).
The tension at the heart of the slow switching intuition is that slow switching both does and doesn’t supervene on objective facts.