The President Has Made Selfishness Our National Credo

Back in the early 2000s, an academic named Robert Sampson did one of the better-known studies in urban sociology of the past 20 years, discreetly dropping thousands of stamped and addressed letters all over the streets of Chicago. What he was looking for, essentially, was to see which neighborhoods would be most diligent about dropping those letters in mailboxes rather than allowing them to collect footprints on the sidewalk and turn to pulp.

What he discovered was intriguing. One of the best predictors of a letter’s fate had to do...