This epilogue is at least in part the result of an accident: a happy one, I hasten to add. A little while back, I was sitting on a panel with the philosopher Christopher Hamilton, discussing the question of whether a world without pain is an appropriate goal for mankind or whether pain serves some additional positive purpose other than the obvious biological one of directing us away from things that might harm us (a topic, perhaps, for a future essay). Meeting Christopher after a long interval reminded me of his excellent book Living Philosophy (2001). The volume includes a fascinating essay entitled “The Need to Sleep”, where he notes that philosophers have not paid sufficient attention to this extraordinary phenomenon. Well, a decade on, this is the beginning of a response to Christopher's wake-up call.

For sleep is rather extraordinary. If I told you that I had a neurological disease which meant that for eight or more hours a day I lost control of my faculties, bade farewell to the outside world, and was subject to complex hallucinations and delusions – such as being chased by a grizzly bear at Stockport railway station – you would think I was in a pretty bad way. If I also claimed that the condition was infectious, you would wish me luck in coping with such a terrible disease, and bid me a hasty farewell.