Themes are the fundamental and often universal ideas explored in a literary work.

Fear of the Unknown

By establishing an area of Ember referred to as the Unknown Regions, the Builders instilled a fear of the unknown in Ember’s future citizens from the very beginning. Those first citizens came to Ember as babies, and their caregivers were old people who were forbidden to bring any items into Ember that might hint at the existence of an outside world. The next generation’s parents would be parented by their biological parents, who taught them only what they knew, and all they ever knew was Ember.

School children learned from The Book of the City of Ember until they were old enough to work at the age of twelve, insuring that the workforce was capable enough to keep the city alive but ignorant enough to fear the unknown and not venture out into it until it was safe enough to do so. The dark is inherently unknowable, and by shrouding the city in darkness the Builders were able to play upon the innate human fear of it to execute their plan to save humanity.

Greed

The Builders took human nature into account when they created a city surrounded by darkness and used fear to ensure that its citizens remained there. They did not, however, account for greed. This human failing is perhaps as big of a threat to the people of Ember as the possibility of them learning about the world outside before it is safe to return. 

Even though he didn’t know what it contained, the seventh mayor of Ember’s desire to survive led him to break his promise and jeopardize the box and its contents. Mayor Cole did not know of the box at all, but his greed led him to hoard the city’s scarce resources at a rate that far outpaced his personal needs, all while his constituents scraped by. Looper and Lizzie’s faulty logic that they might as well enjoy it while they can would only increase consumptions of already scarce supplies. Unlike Lina, who in Chapter 14 wonders if the mayor will enjoy sitting alone in his storeroom once the generator breaks, they do not stop to think beyond their present-day desires.

The Importance of Family and Community

The first families of Ember were created artificially by the Builders in order to ensure that no one would have memories of a world outside of it. The first group of babies grew up to parent their own children, who would embark on their life’s work at the age of twelve. Going to work and committing to a career path at such a young age likely guarantees that the bonds at the workplace are as deep as they are at home, an important way to make sure that everyone in Ember does their job well and that the city survives.

Family and community are important on an individual level as well. Lina is a child with very adult responsibilities and an orphan, so it is crucial that she have other adults in her life that she can rely on, especially once Granny dies. Lina does not ask for help from Mrs. Murdo or from Clary, but they both offer it freely, and once she benefits from their compassion Lina realizes how valuable it is. Clary is the one person that Lina can trust with her message about leaving Ember, and even though she cannot choose who will receive the amended version that she and Doon throw down into Ember in Chapter 20, it is fitting that Mrs. Murdo is the one to find it.