"The oldest answers to the most basic questions about how to operate are common to virtually every culture on the planet, because at the simplest level, every culture needs to keep order -- especially this kind: (James Burke displays a wedding ring.) This is one of those things in life we protect most against being changed when knowledge changes us. We protect it by turning it into a ritual. When we get married, or buried, get christened, or anything else too important to play by ear, the event is turned into a kind of play where everybody gets a role they act out. It's a kind of public agreement to stick to the general rules about whatever it is. The people doing it are effectively saying, "No matter what else may change, we won't rock the boat! We're not maverick. You can trust us." Expressions of approval follow. Most of these ritual ways of answering a social need that we got from the past look like it. They include something from an ancient rite -- in this case, the old symbol of fertility: the ring. And then, it's all done in the presence of a supernatural being: a God. So, the agreement is also made under what was once a real threat of heavenly retribution if you broke your promise later on. Some things, this ritual says, must be permanent."