Chloë: The future is all programmed like a computer – that's a proper theory, isn't it? [...] But it doesn't work, does it?
Valentine: No. It turns out the maths is different.
Chloë: No, it's all because of sex.
Chloë: That's what I think. The universe is deterministic all right, just like Newton said, I mean it's trying to be, but the only thing going wrong is people fancying people who aren't supposed to be in that part of the plan.
Valentine: Ah. The attraction that Newton left out. (2.7)