Fred W. Riggs developed the Fused–Prismatic–Diffracted (FPD) models as part of his broader ecological approach to the study of public administration, particularly to explain administrative systems in developing countries. Riggs was dissatisfied with the direct application of Western administrative theories to non-Western societies because such theories were rooted in socio-cultural contexts that differed sharply from those of developing nations. His models attempt to analyze the relationship between administrative structures and the surrounding social, economic, political, and cultural environment, emphasizing that administration cannot be understood in isolation from society. The fused model represents traditional, pre-modern societies in which social structures are largely undifferentiated. In such societies, political, administrative, economic, religious, and social functions are fused together and performed by the same institutions or authorities. There is little specialization of roles, and authority is usually personal, hereditary, or based on tradition. Administration in the fused model lacks clear separation between public and private interests, and rules are informal, customary, and often sacred. Loyalty is personal rather than institutional, and decision-making is influenced by kinship, caste, clan, or religious norms. Riggs associated this model with agrarian societies where subsistence agriculture dominates and social change is slow. In the context of developing countries, remnants of the fused model persist in rural areas, traditional institutions, and informal power structures, even after the introduction of modern administrative frameworks. The diffracted model represents the other extreme and corresponds largely to advanced, industrialized societies. In this model, social structures are highly differentiated, meaning that different institutions perform specialized functions. Politics, administration, economy, religion, and family operate within clearly defined boundaries. Bureaucracy in the diffracted model is rational-legal in character, guided by formal rules, merit-based recruitment, functional specialization, hierarchy, and impersonality. Authority is institutional rather than personal, and public administration is clearly separated from private life. Riggs viewed the diffracted model as characteristic of developed countries, where social change has led to high levels of structural differentiation, social mobility, and functional autonomy. This model reflects the ideal-type bureaucracy described by Max Weber and serves as a benchmark for administrative efficiency and predictability. Between these two ideal types lies the prismatic model, which Riggs considered most relevant for understanding developing countries. Prismatic societies are transitional societies that exhibit characteristics of both fused and diffracted systems. They are neither fully