Now Christopher explains why he never lies – it isn't because he doesn't want to, it's just that he doesn't know how.
A lie, he explains, is something that didn't really happen. And when he tries to think about something that didn't really happen, he starts thinking about all the infinite possibilities for things that didn't really happen. And it makes him feel "shaky and scared" (37.4).
We'd love to borrow this kid's imagination for an afternoon.
Anyway, this is why Christopher doesn't like novels (boo!). And it's also how we know everything in this book is true.