  Since externalism with respect to justification contrasts with internalism, we should expect there to be an externalist contrast to mentalism. The denial of mentalism would simply be the view that holds that something other than mental states of a cognizer can qualify as genuine justifiers. Once again we can illustrate such a position by considering a reliable process theory of justification. On that theory reliability is defined across mental states, so one might think that the theory is either mentalist or that at least it strongly overlaps the mentalist doctrine. That is, the theory directs our attention to belief-formation processes and belief-sustaining processes, and both of them take some mental states as inputs and yield other mental states as outputs. The simplest version of the former might be a perceptual case in which the inputs are sensory states and the outputs are beliefs. Or, if one thinks of the process of reaching a new belief through reasoning, the inputs are some prior beliefs and the outputs are new beliefs. The difference between this theory and mentalism comes in the fact that for reliabilism the inputs and outputs, though certainly mental, are not themselves justifiers. These inputs are, of course, highly relevant to the justification of the belief. However, this relevance does not suffice to make the inputs justifiers, any more than possession of relevant concepts needed to understand a belief would count as a justifier for that belief. Rather, it is the reliability of the processes in which these inputs and outputs figure that count as appropriate justifiers. So, in addition to being an externalist theory with regard to accessibility, the reliable process theory is externalist with regard to whether the justifiers for a belief are or have to be mental states. The externalist with regard to this issue insists that they need not be.