Choice
As was true of its predecessor, Insurgent primarily revolves around the theme of choices and the way they can change you. After all, the book's tagline is "one choice can destroy you." In Insurgent, all of Tris's decisions had major consequences, as she decided whether or not to enter dangerous situations, to lie to Tobias, and even to sacrifice herself. With so much on the line, Tris's choices affect not only her, but everyone around her. As the series goes on, choice remains just as important, but the stakes get higher and higher.
Division
The entire faction system is based around dividing people up and creating distinct groups with boundaries between them. Insurgent illustrates how these divisions create an "us vs. them" mentality that ultimately brings about disaster. In this novel, schisms also arise within these groups: Dauntless splits into loyal and traitor, Abnegation is scattered, Erudite defect from Jeanine and her following, and Johanna and other Amity split from their faction when they do not agree with the decision to remain uninvolved. These divisions are what ultimately creates so much destruction, and as Tris learns time and again that it is impossible to accomplish lofty goals when you are divided down the middle.
Trust and Honesty
With much of this novel taking place in Candor headquarters, it is to be expected that trust and honesty figure hugely into the theme. Tris and Tobias's relationship is put under strain because of a lack of honesty and an unwillingness to tell each other the truth. In addition, they have problems trusting each other with important things. In most cases each is trying to protect the other, but it results in added distance between them. Surrounding this war are secrets and lies, and while the Candor philosophy is flawed in some ways, in others it makes sense: sometimes the truth really is the most important thing.
War
This novel is a lot darker than the first one, because in reality, what is happening inside the city limits is civil war. People are dying, most of them innocent. Many of Tris's friends are lost, and Tris is forced to kill herself. This novel shows how quickly war can change and mature a person, and how gravely it can tear apart an entire way of life. This may be a futuristic society, but in many ways it reflects the kind of wars we wage in our own world.
Human Nature
A theme of the flaws in human nature is subtle throughout the entire novel, but it is brought to the surface at the end when the video reveals exactly why the factions were created. Though the factions are built around virtues, the people within them are still prone to the vices that plague humanity: greed, guilt, dishonesty, and destructive ambition. It is these vices that cause the rifts in faction society, suggesting that the faction system did not repair the flaws in human nature after all.
Friendship
Though friendship is not quite as central as many of the other themes, many of Tris's endeavors would not have been successful without the help of her friends. Tris was stronger, more confident, and more capable overall after she had Christina's forgiveness; she truly needed her help, and was not the same without her friend in her life. In the Dauntless faction, bonds of friendship are much stronger than they are in any of the others, and that is illustrated through the close relationship between Tris and her friends like Christina, Uriah, and Lynn.
Manipulation
Many of Insurgent's central characters fall prey to intense manipulation, illustrating how powerful coercion can be. The most obvious manipulation is done by Jeanine, both directly through her simulations and indirectly through words, promises, and fear tactics. However, other characters are more discreetly manipulative, too. Evelyn, for example, manipulates Tobias so that she can get the Dauntless on her side and destroy the faction system. It is easy to manipulate others during a war, when everyone is afraid, and everyone has something huge either to lose or to gain.
