"Consider the very roots of our ability to discern truth. Above all (or perhaps I should say "underneath all"), common sense is what we depend on – that crazily elusive, ubiquitous faculty we all have to some degree or other.... If we apply common sense to itself over and over again, we wind up building a skyscraper. The ground floor of the structure is the ordinary common sense we all have, and the rules for building news floors are implicit in the ground floor itself. However, working it all out is a gigantic task, and the result is a structure that transcends mere common sense."