Everything about autism, which is among the most common and the most slippery of mental conditions, is contested. The American Psychiatric Association, which determines what ailments US insurance companies will pay to treat, classifies it as a disorder. Many parents of autistic children are desperately searching for a cure, and find themselves easy prey for people who overpromise, selling remedies that have no scientific basis.

Plenty of other people think that autism – which is characterised, among other things, by an inward focus that makes it hard to abide by the conventions of social behaviour – is not a disorder at all, and therefore has no need of a cure. The US Centres for Disease Control and Prevention thinks that one in 68 children in the United States have at least a touch of autism, which if true means there are more autistic Americans than Jewish ones. This too is contested.