A society that does not laugh is one without an important safety valve, and a society in which people interpret crude humor not as the first step toward friendly relations, but as a mortal offense, is one in which ordinary life has become fraught with danger. Human beings who live in communities of strangers are greatly in need of laughter, if their differences are not to lead to civil war. This was one of the functions of the ethnic joke. When Poles, Irish, Jews, and Italians competed for territory in the New World to which they had escaped, they provisioned themselves with a store of ethnic jokes with which to laugh off their manifest differences.
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The humor-deficit of which Roger writes is most apparent in the academic world.