Ah, so now they're getting to the root of the problem. Or something that's vaguely resembling the root of the problem, because that's an awful lot of bitterness to be a new thing. The Doctor looks down at the scratched boulder. They were lucky this time, it seems.

"And time runs out in the end. The universe just goes up like that," the Doctor snaps his fingers. "No fuss, no blaze of glory; not many people around to even see it. Doesn't mean you can't enjoy what's there."

After all, it's a lovely boulder, Stacy's a lovely, if odd ship, and he does care for all his friends across time and space, even the short-lived ones like the humans. Just because he knows they'll die or he's been to a time period where not only are they dead, but so is the Earth, doesn't mean he'll stop caring. The Doctor tries to figure out what to say to Karis, to show her the world as he sees it. He can give however many speeches he wants, in whatever languages he feels like -- or even musically, like Tir of Antion -- but really, this is one of those things Karis needs to sort out on her own.

The Doctor might dabble in selective non-interference but this? This he'll gladly leave to Karis.