The theme of Silence of the Lambs by Thomas Harris deals with the nature of evil. While the obvious evil is personified in Buffalo Bill and Hannibal Lector, many of the characters and situations in the novel are evil in their own ways. Harris illustrates various types of evil as the FBI attempts to stop a serial killer.
The most obvious forms of evil in the novel are Buffalo Bill and Hannibal Lector. Buffalo Bill kidnaps, starves, and skins women. Hannibal Lector is a serial killer and cannibal imprisoned at an asylum who the FBI turns to for help finding Buffalo Bill.
The conversations Clarice Starling, an FBI trainee, and Lector have often touch on the nature of evil. For example, Lector says:
Nothing happened to me, Officer Starling. I happened. You can't reduce me to a set of influences. You've given up good and evil for behaviorism, Officer Starling. You've got everybody in moral dignity pants—nothing is ever anybody's fault. Look at me, Officer Starling? Can you stand to say I'm evil? Am I evil, Officer Starling?
When she answers that he's destructive, which is the same thing, he offers the counterpoint that if destruction is evil, then storms, hail, and fire are evil—and that all are acts of God. Lector says:
"I collect church collapses, recreationally. Did you see the recent one in Sicily? Marvelous! The facade fell on sixty-five grandmothers at a special Mass. Was that evil? If so, who did it? If He's up there, He just loves it, Officer Starling. Typhoid and swans—it all comes from the same place."
Lector's point, which is carried through the rest of the novel, is that evil isn't always obvious or deliberate. While the evils that Buffalo Bill and Lector pose are studied and deliberate, sometimes evil comes in other forms.
For example, Jack Crawford, the FBI agent in charge of Starling and the Buffalo Bill investigation, is dealing with his sick wife. Though it's not traditional evil, it is a type of evil that fogs his mind as he attempts to work the case. Her illness brings to mind Lector's comment that God causes typhoid. Crawford decides to falsely offer privileges to get Lector to give them information about Buffalo Bill. Though his intentions are good, it allows another problem to take root.
Dr. Chilton, who works at the asylum where Lector is being held, knows that Crawford lied about the transfer. He wants the credit—a selfish motivation—and chooses to offer Lector a different deal that will allow him to move to another institution, which Lector claims to want. While Lector doesn't immediately accept, it sets off a series of events that lead to Lector's escape after he kills his guards.
The characters each want something—promotions, glory, freedom—and work to get those things in ways that aren't completely upstanding. While Buffalo Bill skins women to try to become more like a woman, the rest of the characters all work to their own ends with less gruesome—albeit often unwholesome—methods.
Many of the characters are flawed or make bad decisions in the novel. Ultimately it's left up to the reader to decide what is evil and what isn't. Harris presents a variety of outright chilling evil and more personal, greedy, and false motivations that drive the characters' decisions. No one is completely innocent, and each reader has to judge the characters for themselves.