DETECTIVE TAYLOR: Who gives a f***? He's dead. His wife killed. Anything else has nothing to do with us.
Apathy seems to run rampant in the police force. When Somerset wonders early on if a victim (one unconnected with the murders) has a child who saw anything, this is the response he gets. Somerset is starting to feel this way, too, but this scene shows us that he wasn't always like this.
CAB DRIVER: Where you headed?
SOMERSET: Far away from here.
Somerset's main goal in the movie is just to retire and get the heck out of the city. He hates it. This line isn't even about that, but it shows us that's always on his mind.
SOMERSET: Gentlemen, gentlemen. I'll never understand. All these books, a world of knowledge at your fingertips. What do you do? You play poker all night.
LIBRARY GUARD: Hey, we got culture. Yeah, we got culture comin' out our ass.
Somerset is disappointed that the security guards at the library don't do anything at the library at all. Somerset sees most people like this—more likely to engage in vices (i.e., sins) than doing something productive.
SOMERSET: In any major city, minding your own business is a science. […] Nobody answers to "help." You holler "fire," they come running.
Even though Somerset says this is a problem "in any major city," we have to wonder if he thinks it applies to humanity as a whole. John Doe definitely does.
SOMERSET: You meant what you said to Mrs. Gould, didn't you? About catching this guy?
SOMERSET: I wish I still thought the way you do.
Here, Somerset is disappointed in himself for being disappointed in society. Disappointment-ception. But, maybe Mills' idealism is starting to rub off on him.
TRACY: I'm going around, you know, looking at schools, but the conditions here are horrible. […] I hate this city.
Mills' wife, Tracy, finds a kindred spirit in Somerset. Even though she's only been there a few days, she already hates it. This makes her fate even more tragic. She didn't want to be there in the first place.
SOMERSET: I remember getting up one morning and going to work. It was just another day like any other, except it was the first day after I knew about the pregnancy. And I felt this fear for the first time ever. I remember thinking, how can I bring a child into a world like this? How can a person grow up with all this around them? […] I'm positive that I made the right decision, but there's not a day that passes that I don't wish that I'd made a different choice.
Somerset almost had a baby, too, but he couldn't bear to do it. He knows he made the right decision, but he wishes he hadn't had to make that choice. If the world weren't such a cesspool, he wouldn't have had to.
SOMERSET: But you got to be a hero. You want to be a champion, well, let me tell you, people don't want a champion. They want to eat cheeseburgers, play the lotto, and watch television. [...] I just don't think I can continue to live in a place that embraces and nurtures apathy as if it was a virtue.
Somerset has to be a little more antagonistic to Mills than he does to Tracy because Mills does believe the world can be saved. If Mills found out he was having a baby, he would be happy, and he would do everything he could to make the child's life a good one. But Somerset believes that would be impossible.
MILLS: You say, "The problem with people is that they don't, so I don't care about people." That makes no sense, you know why? […] I don't think you're quitting because you believe these things you say. You don't. I think you wanna believe 'em because you're quitting. […] You want me to agree with you, and you want me to say, "Yeah, yeah, yeah, you're right. It's all f***ed up. It's a f***ing mess. We should all go live in a f***ing log cabin." But I won't. I won't say that. I don't agree with you. I do not. I can't.
This is Mills' takedown of Somerset's apathetic ideology. Unfortunately, it's exactly this attitude that makes him a target.
JOHN DOE: Wanting people to listen, you can't just tap them on the shoulder anymore, you have to hit them with a sledgehammer, and then you'll notice you've got their strict attention.
Recall Somerset's "cheeseburger" quote? Doe is basically saying the same thing. Except instead of sitting around and giving up, Doe wants to do something about it. Unfortunately, that "something" is a series of crazy murders. Maybe being apathetic is the best solution after all.