Domain-general cognitive knowledge has frequently been used to explain skill when domain-specific knowledge held in long-term memory may provide a better explanation. An emphasis on domain-general knowledge may be misplaced if domain-specific knowledge is the primary factor driving acquired intellectual skills. We trace the long history of attempts to explain human cognition by placing a primary emphasis on domain-general skills with a reduced emphasis on domain-specific knowledge and indicate how otherwise unintelligible data can be easily explained by assumptions concerning the primacy of domain-specific knowledge. That primacy can be explained by aspects of evolutionary educational psychology. Once the importance of domain-specific knowledge is accepted, instructional design theories and processes are transformed.