There’s something of a policy revolution afoot: As of March, more than a dozen states — including California, Florida and Ohio — have passed bills or adopted policies that aim to limit cellphone usage at school. More are expected to follow. Jonathan Haidt is the leader of this particular insurgency. “The Anxious Generation: How the Great Rewiring of Childhood Is Causing an Epidemic of Mental Illness,” his book exploring the decline of the “play-based childhood” and the rise of the “phone-based childhood,” has been on the New York Times best-seller list for a year. It feels, to me, like we’re finally figuring out a reasonable approach to smartphones and social media and kids … just in time for that approach to be deranged by the question of A.I. and kids, which no one is really prepared for. So I wanted to have Haidt on the show to talk through both of those topics, and the questions we often ignore beneath them: What is childhood for? What are parents for? What do human beings need in order to flourish? You know, the small stuff. Haidt is a professor at New York University Stern School of Business and the author of “The Righteous Mind” and “The Coddling of the American Mind” (with Greg Lukianoff). His newsletter is called After Babel. This episode contains strong language.