There is a good chance we will soon have a genetic test for detecting the risk of autism in an embryo or fetus.

The development of such a screening tool raises the possibility that parents might one day have the option of preventing the birth of a child with even a mild form of the disorder.

As genetic testing moves into the world of mental health, we are going to face some very tough questions. Will medicine suggest that any and every variation from absolute normalcy is pathological? How can we draw lines between disabling diseases such as severe autism and more mild differences such as Asperger’s, which may give society some of its greatest achievers?