It's amazing how much has always been at stake in the interpretation of these 10 terse phrases.A pair of Supreme Court rulings dealing with the display of the Ten Commandments on public property are only the most recent illustration of the power of the Decalogue (from the Greek, meaning “ten words”) to illuminate philosophical, religious, and cultural fault lines. For two thousand years, it has served as a potent symbol of the clash between moral cultures. The identity of the cultures has changed, but this most familiar of all biblical law codes has remained the ultimate token of victory: He...