  This line of argument depends squarely on a concept of understanding a proposition, and its prospect for success awaits development of a theory of understanding. Even if this can be developed in a promising way, however, it will work only for very simple logical connections. For more complex logical relations and probabilistic ones holding between one's evidence and one's belief, the only available mentalist alternative would be to embrace the idea of awareness of the support relations. This higher order requirement does not seem to be satisfied in all the remaining cases where the support relations have any degree of complexity.