Christianity has never been tried, the cliche runs. And of course it's true, but so is it true that Christianity has checked the movements of millions of men and women who but for the pull of dogma would know no vital brake upon their behavior. Sometimes the brake is effective, sometimes it is not. But that it should be there outweighs any concern over the excesses of Jimmy Swaggart or the ayatollah or the Mormon extremist or the Venezuelan savage--or the European relativist.