Astonishingly irrational ideas are spreading. COVID-19 denial, anti-vaxxers compromising public health, conspiracy thinking hijacking minds and inciting mob violence, toxic partisanship cleaving our nations, the return of Flat Earth theory… What the heck is going on? Why is all this happening, and why now? More important, what can we do about it? Does our “right to our opinion” trump our responsibilities? Does the resulting ethos effectively compromise mental immune systems, allowing “mind parasites” to overrun them? Are conspiracy theories, evidence-defying ideologies, and garden-variety bad ideas all species of mind parasites, each of which employs clever strategies to circumvent mental immune systems? In this conversation, based on the book Mental Immunity, Andy Norman shows that minds and cultures have immune systems, and that they really can break down. Fortunately, he assures us that they can also be built up: strengthened against ideological corruption. Can his ideas revolutionize our capacity for critical thinking?