Thermodynamic miracles... events with odds against so astronomical they're effectively impossible, like oxygen spontaneously becoming gold. I long to observe such a thing.
And yet, in each human coupling, a thousand million sperm vie for a single egg. Multiply those odds by countless generations, against the odds of your ancestors being alive; meeting; siring this precise son; that exact daughter... Until your mother loves a man she has every reason to hate, and of that union, of the thousand million children competing for fertilization, it was you, only you, that emerged. To distill so specific a form from that chaos of improbability, like turning air to gold... that is the crowning unlikelihood. The thermodynamic miracle.
But...if me, my birth, if that's a thermodynamic miracle... I mean, you could say that about anybody in the world!.
Yes. Anybody in the world. ..But the world is so full of people, so crowded with these miracles that they become commonplace and we forget... I forget. We gaze continually at the world and it grows dull in our perceptions. Yet seen from the another's vantage point. As if new, it may still take our breath away. Come...dry your eyes. For you are life, rarer than a quark and unpredictable beyond the dreams of Heisenberg; the clay in which the forces that shape all things leave their fingerprints most clearly. Dry your eyes... and let's go home.
When you run with the Doctor, it feels like it'll never end. But however hard you try you can't run forever. Everybody knows that everybody dies and nobody knows it like the Doctor. But I do think that all the skies of all the worlds might just turn dark if he ever for one moment, accepts it. Everybody knows that everybody dies. But not every day. Not today. Some days are special. Some days are so, so blessed. Some days, nobody dies at all. (In the library, the Doctor walks back to the TARDIS. He stops, looking at the doors. Then he raises his hand, and stands there poised like that for a long moment. Finally he snaps his fingers. The doors open. He smiles slowly and walks in, joining Donna. Then he snaps his fingers again, and the doors close. River's voice continues over this.) Now and then, every once in a very long while, every day in a million days, when the wind stands fair, and the Doctor comes to call... everybody lives.