I don't know whether this is true or not; arguments could (and have) been made that such a skeptic could not exist in a non-empirical void. But that's a bit offtopic, as I still have a problem with your previous sentence: [...] Are you asserting that all things which are "dependent on empirical fact" are "social" ? In this case, you must be using the word "social" in a different way than I am. If we lived in a culture where belief in will-powered flight was the norm, and where everyone agreed that willing yourself to fly was really awesome and practically a moral imperative... then people would still plunge to their deaths upon stepping off of skyscraper roofs.