At the very centre of E. M. Forster's A Passage to India there is a famous encounter with an echo in the Marabar Caves. 'Ou-boum,' says the echo – and to the listener in whom it strikes a strange sort of existential dread, it seems to be saying: 'Everything exists, nothing has value.'
It has always seemed to me that it's the first of these two propositions that's the really interesting one. What if everything really did exist? Somewhere among the ideas that are rattling round in the sub-basement of The Coincidence Engine is that one, tangled up with thoughts about an infinity of parallel universes, half-remembered bits of literary theory, philosophically negligible language-games, and the question 'What is a metre?' – to which nobody knows the answer.
Nobody knows everything, you see. Good old nobody. Quite the smart-aleck.
Long ago, I was bewildered and intrigued to learn that there was such a thing as the 'cardinality of infinities' – which is to say that some infinities are bigger than others. The infinity of whole numbers, for instance, is ipso facto bigger than the infinity of fractions because for every one whole number there are – well, let's just say lots – of fractions in between.
It also titillates me to think that, at the opposite end of the scale, there's more than one different way of not existing. My mum exists. My late grandfather does not exist – at least not in the sense that he did thirty years ago. Unicorns also do not exist – but they don't exist in a different way to that in which my grandfather doesn't exist. And a specific unicorn doesn't exist in a different way to that in which unicorns in general don't exist.
Characters in novels don't exist in a different way, too. And, if you credit the idea that fresh parallel universes calve off from our own at every moment, what about the versions of ourselves that turned left instead of right at the traffic lights? In what way do they not exist? And is it possible that the only reason for our own, fabulously improbable existence in this moment right now is that literally every alternative possibility has been exhausted in the infinity of other universes?
Of course, a lot of this turns on a question of language: as Bill Clinton said, 'It depends on what the meaning of the word "is" is.' But novels are made out of language, and you can do what you like with it in them. My characters live in a universe not too far away from this one – and where ideas and things, past and present, have got just a little bit muddled up.
We all know ghosts don't exist – that nobody comes back to haunt us after death. I find that spooky: 'As I was walking on the stair I met a man who wasn't there.' Or Wallace Stevens in those haunting lines with which he ends his short poem 'The Snow Man'. Nobody's watching: nobody's ever watching.