We can have a sense that when we try to do right by one another, we aren't merely striving against ourselves. The feeling is that we are struggling against something--someone-else. As if there's a force-a person- that wishes us ill. In his letter to the Romans, the apostle Paul describes just such a person: Sin, a cosmic tyrant who constrains our moral freedom, confuses our moral judgment, and condemns us to slavery and to death. Commentators...