 It is fair to note that for Psillos, the fact that a rule-circular argument does not guarantee a positive conclusion about the rule at issue is not sufficient for such an argument to be valid. A further necessary condition is “that one should not have reason to doubt the reliability of the rule—that there is nothing currently available which can make one distrust the rule” (Psillos 1999, 85). And there is plenty of reason to doubt the reliability of IWE; in fact, the above argument supposes that it is unreliable. Two questions arise, however. First, why should we accept the additional condition? Second, do we really have no reason to doubt the reliability of abduction? Certainly some of the abductive inferences we make lead us to accept falsehoods. How many falsehoods may we accept on the basis of abduction before we can legitimately begin to distrust this rule? No clear answers have been given to these questions.