The drug crisis in the United States did not begin with fentanyl. It began with a series of choices that seemed compassionate at the time — prescribing opioids for people in pain, scaling back punishment and trying to make drug use safer. But addiction spread, fentanyl changed the stakes, and the solutions no longer fit the crises unfolding in communities.

Host Megan McArdle talks with Keith Humphreys, a Stanford professor and psychologist, about what America got wrong about drug addiction, why overdose deaths are finally falling, where harm reduction lost its way and what a better approach could look like.