Wright states that the human brain approaches religious belief based on how it adapted to survive and reproduce in early hunter-gatherer societies.

He points out four key traits of religion that align with the human brain's survival adaptations: Humans have adapted to pay attention to surprising and confusing information because it could make the difference between life and death (for instance, if a person left the campsite and mysteriously never returned, it would be wise for the others to be on guard for a predator or some other danger).

Wright uses an example from the Haida people, indigenous to the northwest coast of North America, who would try to appease killer whale deities to calm storms out at sea; they would pour fresh water into the ocean or tie tobacco or deer tallow to the end of a paddle.

Drawing a contrast to such authors as Sam Harris, Richard Dawkins and Christopher Hitchens, Miller gives an overall positive review of the book's approach to the examination of the concept of God.

"[6] Wade replied that "evolution seems to me a sufficient explanation for the moral progress that Mr. Wright correctly discerns in the human condition, so there seemed no compelling need to invoke a deity.

"[6] To promote the book, Wright did a variety of interviews, including with the New York Times,[7] Publishers Weekly,[8] and Bill Moyers Journal.