The Art Institute of Chicago (AIC), one of the world’s finest art museums, harbors (or rather, harbored) 122 highly skilled docents, 82 active ones and 40 “school group greeters.” All are volunteers and are all unpaid. Their job is to act as guides to the Museum’s collection of 300,000 works, which they explain to both adults and schoolchildren. I’ve seen them in action at the Museum, and they’re terrific. Despite the lack of remuneration—they do this to be helpful and because they love art—their training to be docents is extremely rigorous. First, they have to have two training sessions per...