I criticise Cass Sunstein and Adrian Vermeule’s influential critique of conspiracy theories in “Conspiracy Theories: Causes and Cures”. I argue that their position depends on an equivocation over the meaning of the term ‘conspiracy theory’. This equivocation reflects a widespread assumption that conspiracy theories tend to be false, unjustified and harmful, and that, as a result, we can speak as if all conspiracy theories are objectionable in each of these three ways. I argue that this assumption is itself false, unjustified, and harmful. There are many true, justified, and/or beneficial conspiracy theories. This is because people often conspire, we often have good reason to believe that people are conspiring, and there is often a significant public benefit in exposing their conspiracies. I compare conspiracy theories to scientific theories, arguing that just as most of us regard bad scientific theories (i.e. false, unjustified and harmful ones) as an acceptable price to pay for good scientific theories, we should regard bad conspiracy theories as an acceptable price to pay for good conspiracy theories. I go on to argue that Sunstein and Vermeule’s proposed ‘cure’ for conspiracy theories is unlikely to work and is inconsistent with the values of liberal democracy.