[1]
This is the requirement that mental representation be explained without appeal to further forms of representation. If a vehicle is related to its object by convention, the cognitive subject must deploy a rule that specifies how the vehicle is to be interpreted. In the case of non-mental representation, where for example the vehicle is a word in a natural language, the application of such a rule is a cognitive achievement that must be explained in terms of processes defined over mental representing vehicles. When this same account is applied to mental vehicles, therefore, it would seem to generate an infinite regress of further representing vehicles, and hence interpretation is never achieved (see Von Eckardt 1993, p. 206).