INTRODUCTION"Conspiracy theory" is widely used as a pejorative term. An effect of this usage, however, is to discourage certain kinds of legitimate critical inquiry. In a world where conspiracies happen, it is reasonable to seek to formulate good theories of what exactly is happening; and through competent investigation, hypotheses of conspiracy can sometimes be verified. Thus, the general denigration of "conspiracy theory" tends to discourage a kind of practice that there is reason, in fact, to encourage. Of course, this kind of serious inquiry is not necessarily typical of conspiracy theories more generally. Some researchers regard its instances as exceptions to a more general rule whereby conspiracy theories involve unwarranted assumptions and misleading speculation; 1 others maintain-instead or as well-that such investigations as happen to identify a verifiable conspiracy should be exempted from the designation "conspiracy theory" and called something else. 2 However, such suggestions presuppose not only that the grounds of exception or exemption can be clearly specified but also that the specification will be generally understood and applied. But what if neither presupposition turns out to be warranted?That concern is at the heart of this paper: when the pejorative understanding of "conspiracy theory" is allowed to influence policy-making it can serve to legitimate policies whose effect is to impede or even outlaw the kind of civic vigilance that aims to uncover malfeasance on the part of powerful actors. If all kinds of critical and unorthodox inquiry that challenge "official narratives" or institutionally recognized epistemic authorities are potentially liable to be dismissed as "conspiracy theory," then in the event of corruption or capture of institutions this may not only go undetected but could even be protected from detection. The concern is by no means purely hypothetical, and this paper will cite troubling evidence of such an inquiry being not only denigrated and marginalized but actively censored, with those pursuing it being vilified and even persecuted. Accordingly, a central claim here is that the public interest is not well served by general compliance with a default assumption that conspiracy theory should be understood in a pejorative sense.This is an open access article under the terms of the Creat ive Commo ns Attri bution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.