What are the motifs in When the Tripods Came by John Christopher?

Breaking unethical rules is a recurring idea in the story. On several occasions, the narrative refers to characters that cross the boundaries of accepted behavior in the name of independence and freedom, and are rewarded for doing so. This can be seen as a manifestation of the narrative's thematic focus on the value of independent, free thought—specifically, as a suggestion that by breaking the rules, individuals are exhibiting free thought and ought to be rewarded.