What are conspiracy theories? And what, if anything, is epistemically wrong with them? I offer an account
on which conspiracy theories are a unique way of holding a belief in a conspiracy. Specifically, I take
conspiracy theories to be self-insulating beliefs in conspiracies. On this view, conspiracy theorists have their
conspiratorial beliefs in a way that is immune to revision by counter-evidence. I argue that
conspiracy theories are always irrational. Although conspiracy theories involve an expectation to encounter
some seemingly disconfirming evidence (allegedly planted by the conspirators), resistance to all counter-
evidence cannot be justified on these grounds.