Some of the most difficult decisions in law and ordinary life are simplified by the use of some kind of presumption. Accused criminals are presumed to be innocent, and most of the time, legislative acts are presumed to be constitutional. And when people do not know what to do, they often adopt a presumption of some kind—for example, sticking with the status quo, or perhaps in favor of making a specific change. In countless domains, presumptions help people to extricate themselves from difficult situations. They can serve as a way of breaking an initial symmetrical situation by using a supposition not fully justified, yet not quite rash either—favoring one action over the other.