Ethnocentrism--our tendency to partition the human world into in-groups and out-groups--pervades societies around the world. Surprisingly, though, few scholars have explored its role in political life. Donald Kinder and Cindy Kam fill this gap with Us Against Them, their definitive explanation of how ethnocentrism shapes American public opinion.

Arguing that humans are broadly predisposed to ethnocentrism, Kinder and Kam explore its impact on our attitudes toward an array of issues, including the war on terror, humanitarian assistance, immigration, the sanctity of marriage,...