  To the extent that what one is justified in believing depends upon one's evidence, what is relevant is the bearing of one's total evidence. Even if evidence E is sufficient to justify believing hypothesis H when considered in isolation, it does not follow that one who possesses evidence E is justified in believing H on its basis. For one might possess some additional evidence E′, such that one is not justified in believing H given E and E′. In these circumstances, evidence E′ defeats the justification for believing H that would be afforded by E in its absence. Thus, even if I am initially justified in believing that your name is Fritz on the basis of your testimony to that effect, the subsequent acquisition of evidence which suggests that you are a pathological liar tends to render this same belief unjustified. A given piece of evidence is defeasible evidence just in case it is in principle susceptible to being undermined by further evidence in this way; evidence which is not susceptible to such undermining would be indefeasible evidence. It is controversial whether any evidence is indefeasible in this  sense.[5]