"Did you ever count?" the Doctor who isn't the Doctor asks out of nowhere.
"Count what?" he asks. He knows what the old man wants to know, because he remembers this – but he doesn't – and he doesn't want to answer it.
"How many children there were on Gallifrey that day."
That question. The question he never wanted to know the answer to. The question that kept him awake for a week and a half in his leather-clad self, wondering and not wanting to know but needing to know.
"I've absolutely no idea." He's forgotten, he suddenly realizes. He doesn't know. Because finally he's done something right – he's buried the pain of knowing. He's buried it in new pain.
"How old are you now?" Granddad questions. Granddad is nosy. He really doesn't like this man.
He sighs. "Uh, I dunno. I lose track. Twelve hundred and something, I think, unless I'm lying. I can't remember if I'm lying about my age, that's how old I am." Rather impressive it is, too. Twelve hundred years old. Quite respectable to get to this age, he thinks.
Granddad seems shocked. "Four hundred years older than me, and in all that time you never even wondered how many there were? Never once counted?"
"Tell me. What would be the point?" he darts back.
"2.47 billion!" Sandshoes bursts out. He glares at the Doctor, and he can't help but glare back at himself.
"You did count!" Granddad seems shocked again. Rule 1: the Doctor lies. That's always been rule 1, really, ever since the very beginning. How could this one have forgotten? Is this Doctor really the Doctor?
"You forgot! Four hundred years, is that all it takes?" This Doctor understands him best. He still remembers what it was like to be Sandshoes, the weight of the world on his skinny shoulders, the love in his heart, the angst in his soul. He really doesn't miss being him.
This Doctor thought about the 2.47 billion every night. And it nearly destroyed him.
"I moved on!" It sounds like a feeble response even to him. It was the only way he could survive – he forgot, and he had to focus on the people he had with him instead, instead of the people he had lost so many years ago. Even though he knew he was going to watch these die too.
"Where?" Sandshoes demands. "Where can you be now that you could forget something like that?"
River and Amy and Rory and Donna and Martha and Rose and – "Spoilers."
"No, no, no, no, for once, I would like to know where I'm going."
This man doesn't know what will happen. He doesn't know the agony that he will face. The agony that the young, so young, face in front of him has seen.
There's only one thing he can say to this Doctor. Only one thing to justify forgetting his own people to them, the Doctors he used to be. So that they'll know what they will face – love and loss like never before.
"No, you really wouldn't."