Tanzania, March 2 -- You know about Martin Luther, who sparked the Protestant Reformation by nailing his Ninety-Five Theses to the church door in Wittenberg, Germany.

But do you know about his wife, Katie, the runaway nun? He later called her Lady of the New Pig Market because of her efforts to feed the family by raising pigs.

No one thought Martin and Katie could make a good marriage; if you'd done a compatibility test, they're not a match. But why did their marriage work?

Love is a choice: Katie had a quick tongue and Martin had a quick temper, a combination that does not usually make for a good marriage. So what kind of marriage did Martin and Katie have? A very unusual one.

Yes, Katie was outspoken, and Martin had outbursts. But M...