I enjoyed this article very much and thank him especially for several new ideas. And of course, a comprehensive theory of mind must be self-referential. According to KB, the problem with knowledge based on an a priori foundation is that such knowledge is necessarily circular.
Conceptual knowledge is circular.
As a psychologist, I can hardly understand that definition, although no doubt it makes perfect sense in other domains of study, perhaps semantics. If conceptualization is taken as a psychological phenomenon rather than an analytic one, then it is hardly circular. If a discrimination is sensorimotor in nature, the conceptualization may be accomplished and expressed purely in differential behavior, such as approach or avoidance. Conceptualization of a sensorimotor distinction in a socialized linguistic human might just as well be articulated in terms of the network of existing socially defined concepts. It is possible of course to define concepts in terms of other concepts, as a dictionary does, and as hermeneuticists do, and that does constitute formal, closed, circular use of conceptualization.