As the end of the Millennium approaches, conspiracy theories are increasing in number and popularity. In this short essay, I offer an analysis of conspiracy theories inspired by Hume's discussion of miracles. My first conclusion is that whereas Hume can argue that miracles are, by definition, explanations we are not warranted in believing, there is nothing analytic that will allow us to distinguish good from bad conspiracy theories. There is no a priori method for distinguishing warranted conspiracy theories (say, those explaining Watergate) from those which are unwarranted (say, theories about extraterrestrials abducting humans). Nonetheless, there is a cluster of characteristics often shared by unwarranted conspiracy theories. An analysis of the alleged explanatory virtues of unwarranted conspiracies suggests some reasons for their current popularity, while at the same time providing grounds for their rejection. Finally, I discuss how conspiracy theories embody an anachronistic world-view that places the contemporary zeitgeist in a clearer light.