 Externalists also seem vulnerable to the second form of the problem of easy knowledge. They must apparently allow that a circular track-record argument could provide justification for belief in the reliability or trustworthiness of fundamental sources of belief. For example, the reliabilist can rely on perception to justify the reliability of perception, memory to justify the reliability of memory. And it seems implausible that one could acquire justification for the reliability of such sources in this way (see Vogel 2008b for an argument against reliabilism along these lines).