Voltaire's novel [Candid] offers us parallel universes, the possibility of entering into alternative worlds existing side by side, and this is something quite modern. Nested narratives and parallel universes are popular at the moment in many different art forms.

Theatre within theatre, when characters sees themselves on stage, always raises philosophical questions of choice and free will.

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

There is the question of language. Although the play [Candid] is not written in strict verse form, there is an underlying beat of rhyming couplets, with echoes of Pope and the tradition of eighteenth-century philosophical verse.

I have not chosen to create a linear story, but a series of different narratives: in the end there are five plays that almost, but don't quite, add up to one play... I start with the story of Candide, being performed as a play within a play, to bring the audience up to speed with the story.

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.

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.

It's a book that makes me laugh and think - it would be very hard to like someone who didn't enjoy Candide!

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

Rereading Candide, I was struck by the link between optimism and the optimal, the idea that we have been placed in this optimal world rather than some other.

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