In this chapter, Lewis anticipates some of the questions and hesitancies which readers might bring against his argument. In response to his suggestion that human reason is rooted in the eternal reason of God, some might wonder why, then, human minds seem impaired by mere physical circumstance: as for instance, by injury, disability, or the effects of drugs or alcohol. Lewis responds that human minds are not pure extensions of divine reason, but are inextricably physical in their operations, and thus bound by the limitations of physicality: “A man’s Rational thinking is just so much of his share in eternal Reason as the state of his brain allows to become operative” (62).

A second misgiving which Lewis identifies is that which might lead readers to wonder why, if the supernatural exists and exercises such an all-pervasive influence, it is so difficult to perceive. One might suspect that the supernatural should be as obvious to discern as nature itself, especially if it is intimately tied to our own rational operations. But Lewis points out that it is often the most all-pervasive things which escape our awareness: our use of the grammatical rules of our own mother tongue, for instance, or the operations of our faculty of sight—both of which we use all the time without conscious awareness because they are the framework through which we perceive the world.