In 2022 the Belgian clinical psychologist Mattias Desmet went viral when he identified official government policies on the Covid Pandemic as a kind of collective insanity he calls Mass Formation.  Desmet points out that official policies were not modified to conform with scientific findings, instead the findings were ignored and seriously harmful policies were fanatically promoted regardless of the evidence. Many thousands have died because of the lockdowns and the adverse effects of the vaccines. Meanwhile critics and dissenters were demonized and persecuted by methods normally associated with the Salem witch trials or Stalin’s purges.  Desmet’s bold new theory was greeted by Covid skeptics like Robert Malone, Bret Weinstein, and Tucker Carlson with enthusiastic agreement.  Desmet’s numerous social media videos racked up millions of viewers, even before his book, The Psychology of Totalitarianism, became an instant best-seller in all major world languages.  Desmet’s theory of mass formation (sometimes called mass formation psychosis, a label he disavows) explains the official ideology of the lockdowns and vaccines along the same lines as historical pogroms and totalitarian regimes, drawing upon the insights of thinkers such as Gustave Le Bon, Hannah Arendt, and Michel Foucault.  In 1951, Hannah Arendt predicted that the totalitarianism of Stalin and Hitler would be succeeded by the totalitarianism of faceless bureaucratic ‘experts’. This prediction, Desmet claims, is now fulfilled by the fear-mongering and deliberate encouragement of popular ignorance and mass hysteria associated with the Covid lockdowns and vaccines. Ultimately, argues Desmet, we are vulnerable to the craziness of mass formation because we place too much reliance on a mechanistic view of the world and the cosmos and too much trust in the judgment of politically appointed authorities. In Mattias Desmet: Critical Responses, an interdisciplinary group of distinguished writers give us searching criticisms of Desmet’s theory and world-view, from a variety of political and scientific perspectives. In different ways they call into question many of Desmet’s methods, assumptions, and conclusions. Sandra Woien is Senior Lecturer in the School of Historical, Philosophical, and Religious Studies at Arizona State University. She edited the highly-acclaimed anthologies, Jordan Peterson: Critical Responses (2022) and Sam Harris: Critical Responses (2023). Ray Scott Percival is a philosopher who has taught at Lancaster University and the United Arab Emirates University. He founded the Karl Popper Web and the Enlightenment Defended page on Facebook. He is the author of The Myth of the Closed Mind: Understanding Why and How People Are Rational (2012).