I was at an Italian restaurant in Melbourne, listening as a woman named Lesley talked about her housekeeper, an immigrant to Australia who earlier that day had cleaned the bathroom countertops with a bottle of very expensive acne medication: “She’s afraid of the vacuum cleaner and can’t read or write a word of English, but other than that she’s marvellous.”

Lesley works for a company that goes into developing countries and trains doctors to remove cataracts. “It’s incredibly rewarding,” she said as our antipasto plate arrived. “These are people who’ve been blind for years, and suddenly, miraculously, they can see again.” She brought up a man who’d been operated on in a remote area of China. “They took off the bandages, and for the first time in two decades he s...