You find yourself in a court of law, accused of having hit someone. What can you do to avoid conviction? You could simply deny the accusation: 'No, I didn't do it'. But suppose you did do it. You may then give a different answer. 'Yes, I hit him', you grant, 'but it was self-defence'; or 'Yes, but I was acting under duress'. To answer in this way-to offer a 'Yes, but. . .' reply-is to hold that your particular wrong was committed in exceptional circumstances. Perhaps it is true that, as a rule, wrongdoers ought to be convicted. But in your case the court should set the rule aside. You should...