What are the motifs in For Love of Evil by Piers Anthony?

Modes of thinking is a recurring idea. The way that Zane defeats Satan is through using different modes of thinking that Nature points out to him. Zane has been toyed with by Fate, and he has been manipulated by Satan. He has been marked with sin for an act of compassion. All of these forces are outside of Zane, working on him. These forces push Zane along paths he does not want to follow. They interfere with his free will. By showing him the modes of thinking, Nature is bringing Zane back to his free will. He is able to take power from his mind to influence his world.