Few South Africans have heard of Jonathan Haidt, but it’s time they did. His lucid writing on the profound shift in moral culture happening across the English-speaking world has enabled me to make sense of developments that would otherwise be as incomprehensible as they are disturbing.

Haidt, a social psychologist. is professor of ethical leadership at New York University. One of his research fields is the psychology of morality, a concept I had never heard of until I discovered his work. Now that I am familiar with the term, and its many applications, a lot has fallen into place. One is the impact of social media...