First, sorry about that title; I couldn’t help myself. When I was in grad school, a sheltered 21-year-old living on her own in the Big City for the first time, I had a friend I’ll call Bo. An English major like me, Bo was a wildly creative character who scavenged through garbage cans and transformed odd stuff he’d found into some very interesting works of art. He was also eager to share some of the things he regarded as life’s gifts with his friends. And so one day he offered me—a non-smoker, rule-abider, and pretty fastidious sort—a dirty-looking piece of hemp. ....