Today humanity is reaching new heights of scientific understanding – and appears to be losing its mind. How can a species that doubled its lifespan, sequenced its genome, and developed vaccines for Covid-19 in less than a year produce so much fake news, quack cures, conspiracy theories, and “post-truth” rhetoric? In this interview, I speak to Professor Steven Pinker about rationality. We discuss how he rejects the cynical cliché that humans are simply irrational cavemen out of time saddled with biases, fallacies, and illusions (after all, we discovered the laws of nature, and set out the benchmarks for rationality itself). We discuss how we (as a species) think in ways that are sensible in the low-tech contexts in which we spend most of our lives but fail to take advantage of the powerful tools of reasoning we’ve discovered over the millennia: logic, critical thinking, probability, correlation and causation, and optimal ways to update beliefs and commit to choices individually and with others . Steven also takes time to discuss how the rational pursuit of self-interest, sectarian solidarity, and uplifting mythology can add up to crippling irrationality in a society.