Luther Season 1 Episode 2

Alice Morgan: I've been wondering, why do you think he does it?
Zoe Luther: Why does who do what?
Alice Morgan: John, his job. It takes such a toll. Why does he put himself through it?
Zoe Luther: I don't see how this is relevant?
Alice Morgan: Well, it is. Right this second, you might actually be helping him. What do you think compels him to do it?
Zoe Luther: He believes one life is all we have, life and love. Whoever takes life steals everything.
Alice Morgan: And do you agree?
Zoe Luther: I don't know. I think if he'd read a different book by a different writer at just the right time in his life he'd have been a different man. He'd have been happier as a priest than—
Alice Morgan: Than what?
Zoe Luther: Than what he is.