How we cite our quotes: All quotations are from The Departed.
Quote #7
BILLY: Are you trying to say that he was nothing?
COSTELLO: I'm saying he worked at the airport.
Billy doesn't drop the point after Costello insults his dad for having no ambition. He likes to think that his dad was still a somebody, even though he worked at the airport. Costello doesn't really care enough about the point to argue it, so he just lets it go. He has more important stuff to worry about.
Quote #8
BILLY: With all due respect, Mr. Costello, school is out.
COSTELLO: Maybe someday you'll wake the f*** up.
Costello doesn't mind having Billy working in his crew. But he also knows that Billy has done well in school and has come down in the world if he's working for the mob. He even thinks that Billy might be better off if he went back to school and pursued some more normal ambitions. Then he calls Billy an idiot for letting himself settle for a life of crime.
Quote #9
ELLERBY: Some people don't trust a guy with an immaculate record. I do. I have an immaculate record.
Captain Ellerby is an ambitious dude who wants Colin Sullivan to be ambitious, too. He also says that there are lots of folks out there who don't like people who've always done everything by the book—which is the case with both Ellerby and Sullivan.