Conspiracy theories should be neither believed nor investigated – that is the conventional wisdom. I argue that it is sometimes permissible both to investigate and to believe. Hence this is a dispute in the ethics of belief. I defend epistemic "oughts" that apply in the first instance to belief-forming strategies that are partly under our control. But the belief-forming strategy of not believing conspiracy theories would be a political disaster and the epistemic equivalent of self-mutilation. I discuss several variations of this strategy, interpreting "conspiracy theory" in different ways but conclude that on all these readings, the conventional wisdom is deeply unwise.