Thirty years ago, Bill and I had the chance to spend time with some of the children of Oklahoma City in the days following the bombing of the city's federal building. A little girl we met suggested that we plant a tree in memory of the children killed in the attack. So before we got on the plane for the memorial service, we planted a dogwood in the grounds of the White House. As Bill said at that service, the tree "embodies the lesson of the Psalms—that the life of a good person is like a tree whose leaf do