To summarize the book and to discuss the characters is, inevitably, to discuss the themes and meanings of The Martian Chronicles, for the work is thematically organized. Bradbury structures the book primarily as a commentary on mid-twentieth century American life. In the early encounters between humans and Martians, one idea is repeatedly emphasized—that essentially, in their truest needs and desires, humans and Martians are the same. Their differences are on the surface; their likenesses are the fundamental reality. Those people from Earth who, in one way or another, recognize and affirm these essential likenesses, become the heroes of the book. They affirm values such as family love, imaginative sympathy, cultural diversity, unity with an ecosystem, and the ultimate value of living and continuing life against the opposing forces of greed, the will to power, irrational fear of the different, fear of the imagination, excessive faith in technology, and unthinking exploitation of environments. Bradbury arranges these two sets of related values as choices, showing that one leads to the end of the Earth and that the other might, with good luck, lead to a remnant which could preserve the human race.