This document discusses the development and classification of nursing theories. It defines key terms like theory, nursing theory, philosophy, concept, and conceptual model. It describes the components of a nursing theory as concepts, definitions, assumptions, and phenomena. It also outlines different types of nursing theories based on level of abstraction (grand, middle range, situation specific) and goal orientation (descriptive, prescriptive). Examples are provided of different theorists and their associated conceptual models and grand theories. The stages of theory development and various strategies for theory generation are explained. Finally, barriers to theory development are discussed, including human barriers, knowledge barriers, and conceptual barriers.