Experiential learning methods have been recommended for teaching psychiatric nursing students. What has been lacking to date, however, is a sound theory of knowledge to underpin the concepts involved in this relatively new approach to learning. This paper offers an epistemological theory divided into three domains: prepositional knowledge, practical knowledge and experiential knowledge, as a basis for a theory of experiential learning. After a description of the theory, experiential learning is redefined and the practical issues relating to the theory are discussed. The paper closes with some thoughts on the problems of research in the field of experiential knowledge.