Wormwood has asked if it is essential to keep his existence hidden from the patient. Screwtape replies that it is policy to conceal this fact from humans. Otherwise, they cannot be turned into materialists and skeptics who do not believe in anything they cannot sense. There is always hope that, in time, their science can be manipulated to support belief in devils while remaining closed to belief in the Enemy. The ideal is to produce a "Materialist Magician" who believes in life forces in the world but denies the existence of spirits. In the meantime it is best to keep humans in the dark about devils. Screwtape advises that, as Wormwood's human begins to suspect his existence, he should raise ridiculous images in the patient's mind of "something in red tights" that he cannot believe in.

Screwtape then returns to the subject of how best to use the war to manipulate the patient. The goal is to inflame his passions toward embracing extreme patriotism or extreme pacifism. Generally speaking, extremes of all sorts are useful to the devil, except extreme devotion to the Enemy. Extremists will form and belong to small, exclusionary groups, or coteries, centered around a "Cause." These are factions, secret societies, or cliques that foster pride and hatred of the outer world in the name of their "Cause." Screwtape notes that even a group formed around a good cause, such as the Church, may acquire some of the negative qualities of a coterie. However, he admits that devils have failed to sufficiently corrupt it.

Screwtape suggests that the patient might be induced to become a conscientious objector to the war. But this will not work if the man had pacifistic convictions before the war, is a man of courage (not a coward), and believes he is serving the Enemy through his pacifism. If this is the case, then a different approach is called for. Wormwood should introduce an emotional crisis that thrusts the patient toward extreme patriotism.

Either way, the patient should be encouraged to treat his new extreme as part of his religion. Gradually, religion will become merely support for the "Cause," offering strong arguments for or against the war. The "Cause" will cease to serve a higher purpose. It will become a worldly goal the patient pursues, and faith will become only the means of achieving it. The worldly cause matters more than "prayers and sacraments and charity." This is the devil's objective.