See also Analysis.The Dark Knight.
Themes in 'The Dark Knight Trilogy'Each movie has two conflicting themes in it that struggle against one another - one which takes the form of the villain, and one which takes the form of the villain's downfall.
In Begins, it's about Fear versus Love. Some friends were actually doing a drinking game - take a shot every time something thematically related to love comes up in Begins. It's a lot. Batman has to combat the fear toxin, and how does he do that? By trusting the people he loves - Rachel and the man who comforted him when his parents died. By working with them, and by accepting his past, he is able to overcome his fears and defeat the League of Shadows.
In The Dark Knight, it's Corruption versus Trust. The Joker works as a force of corruption against Batman, Gordon and Dent. How often does Dent keep imploring Gordon and Batman to trust him? And how often do they fail to? This is the main thing that stops them from succeeding in most of their goals - not trusting one another. Their reasons are sound, but that lack of trust is what allows the Joker to plant the seeds of corruption. In the end though, it turns out that Batman's trust in the people of Gotham is what saves him - his trust that their decency over Joker's corruption will win. His and Gordon's trust in one another is also what allows them to stop the Joker from winning - to save Dent's legacy.
And in the Dark Knight Rises, it's Despair versus Hope. When Bane throws Bruce into his prison, he tells Bruce: "Despair needs hope". The main struggle in the movie is about whether or not this is true - whether despair needs hope to thrive, or whether hope can overcome despair, even when all seems lost. When Bruce escapes the prison and discovers that what the inmates chant is 'Rise' he realizes that Bane is wrong - the prisoners don't live in despair, they live in hope that they will escape, which means there is hope for Gotham, and for Bruce. And at the end of it, there is still, indeed, hope left for Gotham, just as there is still love at the end of Begins, and trust at the end of the Dark Knight.
The Batman: Life and Death in 'The Dark Knight Trilogy'
All three films play with the willingness (or otherwise) of the Batman to take a life, whether that be his own, or the lives of his foes. In Batman Begins, Bruce Wayne rejects Ras al Ghuls eye for an eye philosophy, arguing that compassion is all that stands between him and the criminal underworld. Although his subsequent actions (taken in self-defense) result in the apparent deaths of several League members, Wayne demonstrates that he is willing to risk his own life to save his mentor. The Batmans no kill rule is arguably broken at the end of the film, when he refuses to save Ras al Ghul.
By the time of the second film, Gothams underworld is aware that the Batman does not use lethal force, and this possibly diminishes the effectiveness of his interrogation of Maroni. In contrast, the Joker is hired to kill the Batman, and at first seems willing to do so (observe his initial assault on the SWAT van while under the impression that Harvey Dent is the Batman). However, this doesn't happen when it is revealed that the Joker no longer has any intention to kill the Batman, as hes just too much fun. Instead, the Joker seeks to goad the Batman into killing him, thus corrupting the Dark Knight. While ultimately he fails, the Batman is forced to place Dents life in danger to stop him from hurting James Gordon. Finally, the Batman assumes responsibility for Dents crimes, casting himself as the murderer.
The third film focuses on Bruce Waynes apparent death wish, which is foreshadowed throughout the film (Alfreds fear that he wants to fail, Banes (and the prison doctors) observation that he does not fear death, Blakes remark that he may not get a chance to thank him later, Selina Kyles plea for him to reconsider). While Bane casually murders his henchmen and innocents, he is initially unwilling to kill the Batman, as he feels his punishment must be severe. As soon as Bane decides to murder the Batman, he himself is murdered by Kyle, who doesnt share the Batmans code of conduct. Compare this to the Joker, who in refusing to kill the Batman, is spared at the end of the previous film. Ultimately, Waynes fate is life, with him choosing the normal life Alfred and his parents would have wished for him, over an untimely death.