"The expression "sense of humor" was first coined in the 1840s, and the idea that such a sense was a personality trait to be valued developed only in the 1870s. What is the relationship between medieval humoral medicine and this distinctively modern idea of the sense of humor? What has it meant in the past 125 years to declare that someone lacks a sense of humor? Why do modern Americans say it is a good thing not to take oneself seriously? How is...