Quote from Philip Pullman's 'Book of Dust' volume 2 - The secret commonwealth.

It's the oldest human problem, Lyra, an' it's the difference between good and evil. Evil can be unscrupulous, and good can't. Evil has nothing to stop it doing what it wants, while good has one hand tied behind its back. To do the things it needs to do to win, it'd have to become evil to do 'em.

It's a fantasy book but I read the quote last night after watching 'highlights' of the Labour party conference. I wonder if Mr Pullman had the gift of prophecy?