Setting: A dilapidated classroom in an anonymous ghetto neighborhood. A mixture of African-American and latino students in the class. The teacher is white in every sense of the word. Class is unruly.
TEACHER (Yelling): QUIET DOWN! WE HAVE TO GET THROUGH THIS MATERIAL FOR THE STATE-WIDE EXAM!
(the students quiet somewhat)
TEACHER: OK. Now, we've already discussed private goods in the marketplace. But now we are going to talk about public goods. A public good is a common resource that is not owned by any one person but is rather shared by everyone in the community.
DARNELL (an extroverted African-American boy in class): Yo mama a public good!
(Class laughs hysterically)
TEACHER (trying to keep his cool): No, no, my mother is NOT a public good. Alright, Darnell. There are some abstract public goods and clean air is a public good which is a bit unusual, but typically for our purposes in this class we are talking about physical infrastructure.
DARNELL: Mah bad, teach. Yo mama bedroom a public good!
(class laughs even harder now)
TEACHER (Angrier now): NO, NO, NO DARNELL! My mother's bedroom is NOT A PUBLIC GOOD! A public good is something like a ROAD!
DARNELL: A road? Damn, son. Don't you know that a road is both rivalrous and excludable, whereas the two necessary conditions to be a public good are NON-rivalrousness and NON-excludability? Ain't you ever heard of congestion pricing? You ever been on the 405 at rush hour? That shit is rivalrous as a motherfucker!
(class laughs hardest at this)
TEACHER: DAMNIT DARNELL! A ROAD IS ABSOLUTELY A PUBLIC GOOD IT'S A TEXTBOOK EXAMPLE NOW LET ME GET ON WITH MY FUCKING LESSON!
(Tyler Cowen appears)
TYLER COWEN: Actually, Darnell here is right. Though in the past, a road has been seen as a public good, economists now agree that it can function as a private good, and the example of public-private partnerships in which private firms build and maintain roads in exchange for the right to charge entrance fees has borne this principle out both in Spain and even in the nearby state of Illinois.
TEACHER: GET THE FUCK OUT OF MY CLASS, COWEN!
TYLER COWEN: Did I mention that the best jazz flautist in Spain is Rodrigo Dominguez and my favorite Spanish food is arepas con carne?
TEACHER: GODDAMNIT TYLER COWEN! YOU ARE THE MONEYEST ECONOMIST AND A BRILLIANT THINKER ANNNNND YOU KNOW MORE ABOUT EVERY CULTURE THAN I OR ANYONE I KNOW! TO BORROW A PHRASE FROM MY STUDENTS, YOU GETTIN' GOT!
(Teacher shoots Tyler Cowen dead)
DARNELL: Damn, Teach! Ah didn't think you had it in you!
TEACHER (calm, earnest): Well, Darnell, I think we both learned today that you can't judge a person just by looking at him.
postscript: Darnell grew up to own a successful chain of barbershops. His column, "Scene from a _____ Barbershop," runs every other Tuesday and is available courtesy of Universal Press Syndicate.