How we cite our quotes: All quotations are from Star Wars: Return of the Jedi.
Quote #7
THE EMPEROR: I'm looking forward to completing your training. In time you will call me Master.
LUKE: You're gravely mistaken. You won't convert me as you did my father.
THE EMPEROR: Oh no, my young Jedi. You will find that it is you who are mistaken, about a great many things.
Here, Luke's making an argument for nurture over nature. He may be Darth Vader's kid, but he was brought up differently—and far more peacefully.
Quote #8
LUKE: I will not fight you, father.
DARTH VADER: You are unwise to lower your defenses!
When Darth Vader says "defenses" here, he's talking not just about Luke's lightsaber, but also his emotional guard. At this point in the story, he views Luke's compassion as a weakness, just like The Emperor does.
Quote #9
THE EMPEROR: Good. Your hate has made you powerful. Now, fulfill your destiny. Take your father's place at my side.
LUKE: Never. I'll never turn to the Dark Side. You've failed, your highness. I am a Jedi, like my father before me.
THE EMPEROR: So be it... Jedi!
Here, Luke flips the script and makes a case for nature over nurture. By that we mean that Luke still believes his dad's a good dude. That goodness is just buried under years of Imperial brainwashing and a really creepy mask. Strip all of that junk away, and there's still a noble Jedi underneath.