We are now so far advanced in our denial of evil that we want to rationalise it away.

In the business world, the idea of positive thinking is absolutely entrenched.

Optimism and happiness are not the same thing, but they are becoming interchangeable, and it seemed to me that Voltaire's Candide gave me a way into something important happening in modern-day culture.

The title's so upfront. It gives fair warning about the play's content. I'm writing about a kind of disenchantment, an anger, but quite a cool 90's anger, at a time when we're not very good at openly being angry. . . . I don't think I ever thought the title was titillating. I thought it was incredibly catchy. If the play is about the reduction in human relations down to a consumerist rationale, then thematically, the title is entirely linked into the thesis of the play.

Translating Candide into tweets has really deepened my appreciation of his writing - it wouldn't work so well with nineteenth-century authors. Every single sentence in Voltaire seems to advance the story, and yet stand alone as a sound-bite.

Twenty years ago, when you bumped into someone and asked how they were, they would say, 'Mustn't grumble' or 'Getting by': now they feel obliged to say 'Just great!'. In both cases, the reply is just a social nicety, but the framework has changed, it's as if it's become a social duty to express happiness.

Candide is one of those books I read when I was young and that I come back to regularly.