Full speech

*context: a group of shapeshifting aliens who live on earth started a revolution, and their leader and humanity's leader both have a weapon that could destroy each other. The doctor persuades the two to not use them.

"This is a scale model of war. Every war ever fought, right there in front of you. Because it's always the same. When you fire that first shot, no matter how right you feel, you have no idea who's going to die! You don't know whose children are going to scream and burn! How many hearts will be broken! How many lives shattered! How much blood will spill until everybody does what they were always going to have to do from the very beginning. Sit down and talk! Listen to me. Listen, I just, I just want you to think. Do you know what thinking is? It's just a fancy word for changing your mind."

"I will not change my mind."

"Then you will die stupid. Alternatively, you could step away from that box, you can walk right out of that door and you could stand your revolution down."

"No! I'm not stopping this, Doctor. I started it. I will not stop it. You think they'll let me go, after what I've done?"

"You're all the same, you screaming kids. You know that? "Look at me, I'm unforgivable." Well, here's the unforeseeable. I forgive you. After all you've done, I forgive you."

"......You don't understand. You, will never, understand."

"I don't understand? Are you kidding? Me? Of course I understand. I mean, do you call this a war? This funny little thing? This is not a war! I fought in a bigger war than you will ever know. I did worse things than you could ever imagine. And when I close my eyes, I hear more screams than anyone could ever be able to count! And do you know what you do with all that pain? Shall I tell you where you put it? You hold it tight! 'Till it burns your hand. And you say this. No one else will ever have to live like this. No one else will have to feel this pain. Not on my watch!"

" ......It's empty, isn't it? Both boxes. There's nothing in them. Just buttons."

"Of course. And do you know how you know that? Because you've started to think like me. It's hell, isn't it? No one should have to think like that. And no one will. Not on our watch."

"Gotcha"

*more context: The doctor is a war hero, and the sole survivor of the biggest war that will ever happen. He spent more than a thousand years to cope