So the thing to remember, the thing that's most important of all that I might say in this here telling of things is that Noise ain't truth, Noise is what men want to be true, and there's a difference twixt those two things so big that it could ruddy well kill you if you don't watch out. (2.23)
Belief systems are actually choices, and in their misery, the men of Prentisstown have chosen to create a pretty terrible reality. As Todd travels, he finds the other people have chosen to build different lives around Noise.
But a knife ain't just a thing, is it? It's a choice, it's something you do. A knife says yes or no, cut or not, die or don't. A knife takes a decision out of your hand and puts it in the world and it never goes back again. (8.76)
Todd sees his new knife as something more than just a "thing." Rather than seeing that he's the one who makes the choice to kill or not, he thinks that the knife itself calls the shots. This isn't true, of course, which Todd will come to recognize.
But I'm holding my knife.
I swear. I swear right now before God or whatever. If Aaron ever comes in my reach again, I will kill him. I ain't hesitating again. No way. No how. I ain't. I swear to you.
I will kill him.
I'll ruddy well kill him. (12.41-43)
The decision to kill is the big choice in the book. Todd won't become a man until he does (by Prentisstown standards) and he's constantly wrestling with the choice. But rather than doing it, or deciding not to, he only tells us over and over again that he will. Buddy, actions speak louder than words, so this isn't really choice as much as the lack thereof.
"Nice bit of engineering, that bridge was," Tam's going on, like he didn't hear me and maybe he didn't, what with how loud he's talking. "Sad to hear it's gone."
"We had no choice," I say.
"Oh, there's always choices, pup, but from what I hear, ye made the right one." (15.58-60)
This whole idea of choice is really tossed around in The Knife of Never Letting Go. Even though Todd spends most of his time and energy mulling choices over in his head, he always seems to think that there's only one option in the end. Tam reminds him that there isn't, that there's always choice.
I press myself back into the little nook but it's really not wide enough for me. I glance round, seeing where escape might lie.
I don't find nothing much.
My knife's gonna have to do it. It's gonna have to act, even if it's against a machete. (19.65-67)
Todd has this weird idea that his knife has a mind of its own—if he kills, it will be the knife's decision, not his. He imposes this weird power on this knife, which in reality only does what he wants it to.
Maybe our story will turn out differently if we take the left fork, maybe the bad things that are waiting to happen to us won't happen, maybe there's happiness at the end of the left fork and warm places with the people who love us and no Noise but no silence neither and there's plenty of food and no one dies and no one dies and no one ever dies.
Ah yes, the classic dilemma of which path to take. Todd takes a minute and thinks of the outcome of picking what may be the right or wrong path. But this is the type of choice you just have to make, because there are no clues about which one is right. Todd's going to have to pick at random—and hope he survives.
She waves this away. "If they can snuff out that part of you that's good, the part of you that won't kill, then they win, don't you see? If they can do it to you, they can do it to anyone. And they win. They win!" (24.59)
If Prentisstown manages to take away his right to be innocent, then they have everything, so Todd needs to protect himself against their threats and bullying and stand up for what he knows is right. It's all he has to call his own.
The knife is alive.
As long as I hold it, as long as I use it, the knife lives, lives in order to take life, but it has to be commanded, it has to have me to tell it to kill, and it wants to, it wants to plunge and thrust and cut and stab and gouge, but I have to want it as well, my will has to join with its will.
I'm the one who allows it and I'm the one responsible. (31.20-22)
Todd has finally realized that he's the knife-master, that the knife can't do a thing unless he picks it up and makes it. The way he sees it, that knife was made to do destructive things, but it can't actually do so unless he "tells" it to. He has to make that choice and will the knife to bring death.
"But if you and Cillian were innocent—" I start.
"We weren't innocent," Ben says strongly, and suddenly his Noise tastes bitter. He sighs. "We weren't."
"What do you mean?" I ask, raising my head. The sickness in my stomach ain't leaving. "What do you mean you weren't innocent?"
"You let it happen," Viola says. "You didn't die with the other men who were protecting the women." (36.113-116)
Sometimes you're in the wrong because you do the wrong thing, but sometimes you're in the wrong because you don't do the right thing. Ben is explaining that he's at fault for not defending the innocent in Prentisstown. Sure, he didn't take a gun into the street and kill them, but protecting himself while the innocent suffered was a choice—and it wasn't the right one.
"I wouldn't've done it." I say and he scowls at the interupshun. "I wouldn't've killed anyone."
"Ah, yes, Todd Hewitt," Aaron says. "And that's why yer so very special, ain't you? The boy who can't kill." (41.81-82)
Aaron is twisting Todd's motive. Todd has made his choice not to kill. But Aaron is trying to tell him that it wasn't a choice—that instead, Todd wasn't capable of killing. This is a mind trick. Aaron is trying to get Todd to think that he can't make choices, which would mean that everything Todd does comes from whether or not he can, instead of whether or not he wants to.