Both varieties of the coherence theory can be understood in a way that allows them to avoid the problem we noted for experiential foundationalism: each can be taken as a theory of justification for memory beliefs, both dispositional and occurrent (and since negative coherentism and simple foundationalism are essentially the same theory, we will consider simple foundationalism here as well).  Taken as global theories of the justification of memory belief, they claim that any stored belief is prima facie justified.  Yet there other problems that infect both theories.  The primary problem for positive coherence theories is what has been dubbed the “problem of forgotten evidence.” A belief might positively cohere with the subject's belief system at the time the belief was formed but later fail to positively cohere even though it intuitively remains justified.  One might have once had a web beliefs about American history with which the belief that Lincoln was assassinated in Ford Theatre neatly cohered.  Yet years after having had one's last history class, this belief might remain while much of the imbedding web was disappeared.  Yet, intuitively, it is still justified.  The coherentist might hope to reply to this problem by claiming that there is still a justificatory web: the belief is a memory belief and one might believe that most of one's memory beliefs are true; therefore, this belief is likely to be true and is hence justified.  The problem with this response is that it works for just any memory belief; if this gambit is allowed, then every memory belief will be prima facie justified.  That is, accepting this solution to the problem of forgotten evidence amounts to trading in positive coherence theory for its negative sister.