DOCTOR: Never be cruel. Never be cowardly. Hate is always foolish. Love is always wise. Always try to be nice, but never fail to be kind.

FIRST DOCTOR: There is good and there is evil. I left Gallifrey to answer a question of my own. By any analysis, evil should always win. Good is not a practical survival strategy - it requires loyalty, self-sacrifice and love. And so, why does good prevail? What keeps the balance between good and evil in this appalling universe? Is there some kind of logic? Some mysterious force?

BILL: Perhaps it's just... a bloke.

FIRST DOCTOR: A... bloke?

BILL: Yeah! Perhaps it's just some bloke, wandering around, putting everything right when it goes wrong.

FIRST DOCTOR: Well, that would be a nice story, wouldn't it?

BILL: That would be the best.

DOCTOR: I really didn't know. I wasn't sure. You lose sight sometimes. Thank you! I am not a good man! I am not a bad man. I am not a hero. And I'm definitely not a president. And no, I'm not an officer. Do you know what I am? I am an idiot, with a box and a screwdriver. Just passing through, helping out, learning. I don't need an army. I never have, because I've got them. Always them. Because love, it's not an emotion. Love is a promise.

MOMENT: You know the sound the TARDIS makes? That wheezing, groaning. That sound brings hope wherever it goes.

WAR DOCTOR: Yes. Yes, I like to think it does.

MOMENT: To anyone who hears it, Doctor. Anyone, however lost... Even you.

CLARA: Be a doctor. You told me the name you chose was a promise. What was the promise?

TENTH DOCTOR: Never cruel or cowardly.

WAR DOCTOR: Never give up, never give in.

DOCTOR: Look, my name, my real name, that is not the point. The name I chose is the Doctor. The name you choose, it's like, it's like a promise you make. He's the one who broke the promise.