As Screwtape constantly reminds Wormwood, Christianity teaches that humans are unions of bodies and souls. This has far-reaching implications for human nature: Although the soul is eternal, the body exists in time and is therefore subject to changing conditions, appetites, etc., which Screwtape advises Wormwood to exploit. However, the distinction between body and soul is not so simple as a mere division between physical experiences and mental ones, as for an embodied being, mental states (feelings, thoughts, etc.) are also at least partly physical in origin. Nor does the juxtaposition of body and soul imply a moral classification of the physical as “bad” and the spiritual as “good.” Rather, Lewis suggests that the life of the body, broadly understood, can be either a gateway or a barrier to the life of the soul.

The nuances of this position emerge in Screwtape’s discussion of how to tempt human beings. It is a common misconception, Lewis suggests, that Christianity views sensory pleasure itself as sinful. As Screwtape argues, when a human being is directly connected to their experiences, whether that means eating, having sex, or taking a walk in nature, they are more likely to find life pleasurable and to be peaceful and content.