Castiel suppressed a faint laugh in her shoulder. She looked straight at the manipulations of individuals, he saw a larger scale.
"I don't mean each person's vulnerabilities, their weaknesses to be exploited, I mean how vulnerable the city is," his gaze went out over the lights of the city.
"I could smite them all right now, with a thought. They're going amongst their lives, and the fact is they could all be dead within minutes if I chose to. Or if other beings chose to. Every one of them is so small. When they wake up they might crash their car on the way to work. They might develop all kinds of diseases that will eat them from the inside. Maybe they'll do something to themselves like take drugs or get into a fight. Lives snuffed out so fast and yet they never give up. And that's what I see."
He swallowed slightly, feeling the softness of her hair against his face. "Compared to us, they only live for minutes. I know that I will eventually watch Dean die, Sam will die, all of them. I hope and pray that it is of old age, and that they're peaceful and happy when they go, but it'll still be in a blink of an eye for an immortal like us. But I love them anyway, even though it will hurt to lose them."