How to solve a carbon dating problem

You have a Chechen woman in Moscow in early 2004 who blows herself up in the subway station. “You think that terrorists aren’t aware of how easy it is to be characterized by ethnicity? The pit-bull appearance is a proxy for the pit-bull temperament—for some trait that these dogs share.But “pit bullness” turns out to be elusive as well.Figuring out what an Islamic terrorist looks like isn’t any easier. Pit-bull bans involve a category problem, too, because pit bulls, as it happens, aren’t a single breed.

How do we know when we’ve made the right generalization? In July of last year, following the transit bombings in London, the New York City Police Department announced that it would send officers into the subways to conduct random searches of passengers’ bags.

A handler takes a dog on a six-foot lead and judges its reaction to stimuli such as gunshots, an umbrella opening, and a weirdly dressed stranger approaching in a threatening way. “Their stability and resoluteness make them excellent for work with people who might not like a more bouncy, flibbertigibbet sort of dog. More police means that some crimes are prevented, others are more easily solved, and still others are displaced—pushed out of the troubled neighborhood—which Kelly says is a good thing, because it disrupts the patterns and practices and social networks that serve as the basis for lawbreaking.

Eighty-four per cent of the pit bulls that have been given the test have passed, which ranks pit bulls ahead of beagles, Airedales, bearded collies, and all but one variety of dachshund. When pit bulls set out to provide comfort, they are as resolute as they are when they fight, but what they are resolute about is being gentle. has done, under Commissioner Kelly, is to use the map to establish “impact zones,” and to direct newly graduated officers—who used to be distributed proportionally to precincts across the city—to these zones, in some cases doubling the number of officers in the immediate neighborhood. In other words, the relation between New York City (a category) and criminality (a trait) is unstable, and this kind of instability is another way in which our generalizations can be derailed.

A doctor could, with some statistical support, generalize about men of a certain age and weight.

But what if generalizing from other traits—such as high blood pressure, family history, and smoking—saved more lives?