In Part II, Question 2 of the Malleus Maleficarum (The Hammer of the Witches), the 15th century witch hunter's manual, the authors ask:
Is it lawful to remove witchcraft by means of further witchcraft, or by any other forbidden means?
This is a variation on the question concerning means and ends, but with a poetic twist. In the standard form of the question, we evaluate the two terms and try to determine if the good we seek to accomplish is greater than, or less than, the evil that is required to accomplish it, and if the answer is yes, then we call these means a necessary evil. In the form posed by the Malleus Maleficarum, there is a more direct relationship between the means to be used and the evil to be overcome. They are neither greater nor less than, but are in fact identical to the evil to be overcome.
In metaphysical jurisprudence, Dante calls this relationship between the crime and the punishment contrapasso, or the counter-suffering that a soul suffers for the sins he committed in life. Through this principle, people in sinning choose their own meet punishment in the afterlife, and the cosmic order is maintained. Thus, Paolo and Francesca, who were caught up in each other's lust in life, are caught up in in an eternal whirlwind in the afterlife, and the epicureans, who insist that the soul is permanently tied to the body, are forced to drag their bodies around in hell.
This poetic principle which assures justice with regard to punishment, because it makes the punishment always fit the crime, has a jarring effect when applied to practical reasoning and police work, which occur before any punishment is necessary. By using the means of the enemy we seek to overcome, we somehow perpetuate the evil that we seek to destroy. Cosmically, this evil is somehow transferred to us. It is a standard trope of science fiction that when we use the tools of our enemy, we become no better than our enemy.
There is a direct relationship between the witch-hunting of the 15th century, and the cold war of the 20th. Not only were we similarly caught in a general fear about an enemy that we were not certain we could overcome, but the same temptations about the tools to be used were raised by the nature of the conflict. Deviousness and ruthlessness, an absence of morality, are the greatest strengths of the enemy. To what extent must we suspend our own morality in order to defeat this enemy? And having done so, to what extent are we still the good guys.
In the 15th century, the advice to witch-hunters was to not use the tools of the witches. In the Malleus Maleficarum, this is stated as an absolute prohibition, with the explanation that any attempt to use magic will either directly call upon the aid of demons, or will open the practitioner of such means up to the influence of the demons.
In the 20th century, we were more accommodating toward the Devil. In The Spy Who Came In From The Cold, John Le Carre places the following words in the mouth of Control, the head of the Britain's Secret Service, who is explaining to the hero, Alec Leamas, why he must go on just one more mission:
"Thus we do disagreeable things, but we are defensive. That, I think, is still fair. We do disagreeable things so that ordinary people here and elsewhere can sleep safely in their beds at night. Is that too romantic? Of course, we occasionally do very wicked things"; he grinned like a schoolboy. "And in weighing up the moralities, we rather go in for dishonest comparisons; after all, you can't compare the ideals of one side with the methods of the other, can you, now?"
Leamas was lost. He'd heard the man talked a lot of drivel before getting the knife in, but he'd never heard anything like this before.
"I mean you've got to compare method with method, and ideal with ideal. I would say that since the war, our methods -- ours and those of the opposition -- have become much the same. I mean you can't be less ruthless than the opposition simply because your government's policy is benevolent, can you now?" He laughed quietly to himself: "That would never do," he said.
But if our actions are justified because we are the good guys, at what point are we no longer able to distinguish ourselves from the bad guys and suddenly find ourselves in Hegel's verkehrte Welt, the inverted world in which we are no longer ourselves? This is a question that is raised with great regularity in modern politics, in world affairs, and in our daily lives. The problems of the topsy-turvy world arise when we begin to practice a negative ethics rather than a positive one, in which we are defined much more by what we are not, rather than by what we are.