"If you want to take it to a higher authority, then there isn't one. It stops with me."

Did Rose hear him? He doesn't dare ask. Even for him, this is beyond hubris. And yet… it's true. Who else can fight the battles to come? Gallifrey is gone, the Guardians will not interfere, and Deity — if Deity exists — remains silent. Only he remains, Lord of Time and Pawn of Fate. He dares not think too much about his own fallibility, lest he falter in his task.

There is no higher authority. He wishes there were a better one.