Self-Sacrifice
Self-sacrifice is a theme throughout this novel and becomes the model for heroism. Among many distasteful and unethical characters, the ones who distinguish themselves are those for whom the contagion becomes an unavoidable personal crisis. Characters like Wolgast, Amy, and Sister Lacey invest in the well-being and survival of humanity as a species, consequently devoting their own lives to the preservation of the people around them. For Wolgast, self-sacrifice takes the shape of a personal quest. He sees that Amy is powerful and may help save people, so he, in turn, lives his entire life as her protector and advisor, severing his ties with both the government and Dr. Lear's program. Both Amy and Sister Lacey physically subject themselves to suffering, torture, and death in order to defeat Babcock and eliminate the immediate threat.
Violence As a Function of Vengeance
In all his research, Dr. Lear forgets to take into account the human element of human experiments. He chooses men who have a previous history of extreme violence and makes them physically powerful. It's not a good combination. When Babcock realizes his psychic powers, he uses them exclusively to inflict pain on normal people. His life narrative is solely about vengeance. His biggest target becomes Lear himself, as the representative of the dehumanization to which Babcock has been subjected all these years -- within society, within the prison system, and definitely as a part of Lear's research program. When he kills Lear, Babcock, unsatisfied, then directs his violent rage at everyone.
The Vulnerability of Human Relationships
Most of the characters in this story, understandably, struggle to relate to other people. When the entire world is caught in the midst of a decades-long traumatic outbreak, one must assume people will struggle to trust one another. Sister Lacey is the character who most strongly speaks against this concept. She deliberately ignores personal threat to preserve relationships, namely with Amy. Observing Lacey's example, Wolgast follows suit and devotes himself to Amy as well. As the recipient of love, Amy grows up into a fierce warrior who is determined to help people. She directs the fullness of confidence, stability, and authority which she carries outward, in the hopes of fostering love and community.
