The philosophical interest in political conspiracy theories is a rather recent phenomenon. Although philosophers have always been interested in conspiracies—Niccolò Machiavelli and David Hume, for example, studied them—not much has been written about conspiracy theories. However, conspiracy theories and conspiracy theorizing have recently gathered a considerable amount of attention among a number of disciplines, including philosophy, sociology, history, law, psychology and political science. This special issue of Argumenta delves into the ethical and epistemological questions of political conspiracy theories.