There’s still so much we don’t know about dreams . What shapes them? What is their true purpose ? Wanting to understand such questions, I headed to the Arizona desert for the 35th annual International Dream Conference in Phoenix, last month, only to find myself having lunch with a psychoanalyst scheduled to give a talk on using dreams to predict the future. I was lucky not to choke on my burrito.

The International Association for the Study of Dreams, which runs the conference, is “multidisciplinary”: it embraces both scientific and other modes of enquiry …