  Externalism is also supported to varying degrees by any cogent criticisms that have been devised against internalism. On this score, too, it is accessibility internalism that is especially vulnerable, particularly in the face of the perceptual examples already considered in which many justified beliefs are received either simultaneously or in rapid order.Further, there is the dilemma argument which poses a particularly forceful challenge to access internalism. Mentalism is only marginally better off in this regard, because as we noted earlier, the evidential support relations that obtain between justifiers and resulting beliefs seem themselves to be justifiers though they are not mental states. Even if we allow that in simple cases one's justification for a belief that follows immediately from one's understanding of simple premises from which the believed proposition follows, this sort of strategy will only work in a small class of cases. Wherever the evidential support relations are more complex, mere understanding of the propositional content of the justifiers will not suffice to issue in justification for a resulting belief. In other words, the above-discussed criticism of the mentalist position concerning probabilistic relations, while perhaps not wholly effective, nonetheless has force against all but the simplest of cases, and to that extent the case for externalism is strengthened by the weakening of the support for mentalism.