Arguing that an explicit representation of the problem-solving method of an expert system shell as abstract control knowledge provides a powerful foundation for learning, this paper describes the abstract control knowledge of the Heracles expert system shell for heuristic classification problems, and describes how the Odysseus apprenticeship learning program uses this representation to automate "end-game" knowledge acquisition. Particular emphasis is given to showing how abstract control knowledge facilitates the use of underlying domain theories by a learning program. Three figures and one table are provided. (16 references) (Author/EW)