All people need to make decisions from time to time. Given limited time in formulating policies and addressing public problems, public administrators must enjoy a certain degree of discretion in planning, revising and implementing public policies. In other words, they must engage in decision-making (Gianakis, 2004). Over the years, many scholars tried to devise decision-making models to account for the policy making process. All people need to make decisions from time to time. Given limited time in formulating policies and addressing public problems, public administrators must enjoy a certain degree of discretion in planning, revising and implementing public policies. In other words, they must engage in decision-making (Gianakis, 2004). Over the years, many scholars tried to devise decision-making models to account for the policy making process. Since the development of public administration, scholars have assumed that people make decisions rationally. By rationality, ] (1976) means ”a style of behaviour that is appropriate to the achievement of given goals, within the limits imposed by given conditions and constraints” (P. 405).Max Weber, in the early part of the 20th century, suggested distinguishing two types of economic rationality: formal rationality and substantive rationality. The 'formal rationality of economic action' referred to 'the extent of quantitative calculation or accounting which is technically possible and . . . actually applied.' 'Substantive rationality' referred to the degree to which economic action serves 'ultimate values no matter what they may be.' (Weber, The Theory of Social and Economic Organization, Parsons, ed., 1947, pp. 184-186) Weber noted that 'the requirements of formal and of substantive rationality are always in principle in conflict.' (Ibid., p. 212) Decades later, Simon used a similar terminology to distinct two meanings of 'rationality', which have developed separately in economic and psychology. He defined substantive rationality, stemming from the concept of rationality within economics, as behavior that 'is appropriate to the achievement of given goals within the limits imposed by given conditions and constraints'. Procedural rationality, based in psychology, refers to behavior that 'is the outcome of appropriate deliberation'.