Ed Koch, New York City's voluble mayor, recently recounted how he had toured Manhattan in the company of some mental health experts. Concerned about the mentally ill who live on the streets, Hizzoner had decided to do some sidewalk research. On the tony Upper East Side, the group encountered a bedraggled, incoherent woman lying in the street, having thoroughly soiled herself. The woman could not be forcibly committed to a mental health institution, said the experts, because she did not present an "imminent danger." Koch was stunned, and recalled thinking, "You're loony yourself."
A normal, common-sense reaction, certainly, but one with...