The popularity of conspiracy theories poses a clear challenge for contemporary liberal democracies. Conspiracy theories undermine rational debate, spread dangerous false-hoods and threaten social cohesion. However, any possible public policy response, which would try to contain their spread, needs to respect the liberal commitment to protect pluralism and free speech. A successful justification of such a policy must therefore: 1) clearly identify the problematic class of conspiracy theories; and 2) clarify the grounds on which the state is justified in acting against them. This article argues that the prevailing epistemic approaches to conspiracy theorizing cannot fulfil these criteria. Defining conspiracy theories by their flaws in reasoning, questionable coherence or factual mistakes can neither sharply distinguish problematic conspiracy theories from other, non-problematic worldviews nor justify state action. Thus, we propose to understand conspiracy theories through their ethical unreasonableness. We hold that containment of conspiracy theories is justifiable insofar as they undermine the liberal-democratic ideals of mutual respect, freedom and equality. We then show that such 'ethical' criteria for conspiracy theories can be sufficiently robust and clear-cut so that they can serve as a useful guide for public policy.
