Professor Armen Alchian, a very distinguished economist, used to give me a hard time in class. But one day, we were having a friendly chat during our department's weekly faculty/graduate student coffee hour, and he said, "Williams, the true test of whether someone understands his subject is whether he can explain it to someone who doesn't know a darn thing about it."Here's a link to the first one (you can find links to the others on the right hand sidebar in the article).
Economics for the Citizen (Part 1) by Walter Williams