rosa mundi
It's necessary for him to remember the small things. Little things like single lives are easy to forget, and add up so very quickly. Whether it's right or not to limit himself, to weigh single lives against whole worlds, is beside the point. He has chosen to care. He must remember to do so.
There have been times when he's wanted to be the manipulator, the player of games. This isn't one of them.
That's why he invites her into the TARDIS. Ah, Rose, sweet Rose, rose of earth, rose of the world, rosemary, that's for remembrance; pray, love, remember.
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