Excerpt from Us and Them by David Berreby, plus links to reviews, author biography & more

These nonliteral ways of saying "we" aren't logical, but obviously they aren't meaningless. People understand them, and distinguish them from nonsense. That means people use some set of rules to decide that a sentence like "We Americans fought a war with Spain" is comprehensible, while "We left-handed folk are a generous people" is twaddle. These aren't the rules of science, but so what? They do different work for the mind and heart.

Language, though, has its own rules, which don't respect this distinction. Grammar doesn't reveal when we're speaking logically and when we're speaking - often with the same words - in the special code of human kinds. So we're inclined to think the same word means the same thing all the time. That hunch is wrong. The way it's wrong reminds me of the story of an awkward lunch in 1944 where the British prime minister, Winston Churchill, met Mr. Berlin.

Isaiah Berlin, the philosopher and historian, had been serving as a diplomat in New York and Washington. Churchill had been impressed with his work. He asked: "Berlin, what do you think is your most important piece you've done for us lately?"

A little hesitantly, his guest replied: "'White Christmas.'" He was the wrong Mr. Berlin - Irving, the songwriter, not Isaiah, the polymath. In that instance, one word - Berlin - certainly did not mean one thing. Human-kind words often exhibit this variability. Just as a screwdriver in the toolbox is different from the screwdriver you order from a bartender, so "we" in a sentence like "We Americans beat Spain in a war" is different from the "we" in "We Americans number about 290 million."

One of those two meanings - we the citizens of the United States, as defined by law, who are alive today - fits into the framework of science. It describes physical objects that can be measured. The other idea - we Americans, including people who no longer exist because they died a century ago; we Americans, including people who did not experience the war - comes out of different rules for defining we.

If human kinds have their own rules, separate from those of logic or human institutions, and if those rules operate outside of our awareness, then the scientific study of human-kind beliefs will have some weird implications. For one thing, trivial, meaningless, ephemeral human kinds - if they meet the requirements of the hidden rules - could make and unmake people's lives with the same force as the human kinds we respect, like religions, nations, and ethnicities.

It's a strange idea. Could human kinds like "Star Trek fan" and "Porsche owner" ever weigh as heavy in a human heart as a religious tradition, with all its culture and moral seriousness? If that were so, then history would afford examples of oddball academic ideas that turned into the basis for mass murder; it would include instances of people changing their lives, even killing and dying, for sports teams or handkerchiefs.

Most peculiar. Yet this has happened throughout history. That too is part of the evidence that human kinds have a separate realm in the mind.

In the nineteenth century, linguists and anthropologists took a Sanskrit word for noble and turned it into a term to describe a family of ancient languages. So the human kind called "Aryans" was born. Languages were all it referred to, wrote the German scholar Max Müller: "I have declared again and again that if I say Aryas, I mean neither blood nor bones, nor hair, nor skull." Nonetheless, as Müller's protest shows, this academic term quickly took on tribal trappings. A few decades later, reinforced by other newly created human kinds, like National Socialist and "expert" on Jewish matters - assigned by law to every government office under Hitler - Aryan was a life-and-death human kind. Nowadays, in the form of gangs like the Aryan Brotherhood in American prisons, it continues to be a category that gets people killed.

Copyright © 2005 by David Berreby.  No part of this book maybe reproduced without written permission from the publisher.