Many scholars have characterized conspiracy theories as self-sealing. That is, they are immune to disconfirmation, since conspiracy can always explain away counterevidence. This is thought to make belief in them irrational. However, the potential to escape disconfirmation by modification of a theory, or of related auxiliary hypotheses, is a feature common to all theories, including scientific theories. Further, attempts to rescue theories from disconfirmation often come at an epistemic cost. More specifically, such attempts, to the degree they seem ad hoc, tend to lower the theory’s credibility. Those who characterize conspiracy theories as “self-sealing” tend to ignore the implication of this. Namely, the fact that conspiracy theories may theoretically resist refutation (a fact shared by all theories) does not mean that they are immune to all standards of evaluation. Individual conspiracy theories should be evaluated on their various individual qualities. This includes the degree to which a particular conspiracy theory depends on positing an implausible cover-up. Such a dependence is, indeed, a consideration that may potentially weigh heavily against that individual theory. But such a judgment will need to take into account the reasons given in support of the particular postulated cover-up, as well as other relevant considerations.