People who participate in policy-making, from government, academia, industry and civil society, would all prefer their perspectives be regarded as rational. There is little agreement, however, on what comprises rationality, with conflicting claims of 'scientific sense' and 'democratic sensibility', and disagreement on whether moral considerations are part of rational decision-making. Pragmatist philosopher John Dewey drew from the natural and social sciences, as well as his international political experience, to describe rationality as a characteristic of human agency. He posited that rationality should comprise scientific sense, democratic sensibility and moral imagination in order to resolve problematic situations and support individual and social flourishing. In instituting contemporary policy science, Harold Lasswell considered pragmatist philosophy to be its foundation. However, this pragmatist perspective has since been overlooked. Policy science developed with a primarily empirical focus on discrete aspects of policy-making. There is now an identified need for more integrative and normative theories to better understand and guide public policy. The primary goal of this thesis is to demonstrate that rationality, as defined in pragmatist philosophy, can integrate diverse considerations of policy theory and public participation. In order to make the philosophical concepts more operative, a new theory of policy-making - the Decision Cell 3 model - is developed. This model is structured according to key 'pillars' of pragmatist philosophy and shaped by contemporary theoretical and empirical analyses, particularly of health policy. Primary research on the impact of health services and policy research at LSHTM, and on UNICEFcivil society organisation partnerships with respect to children's rights, further informs the development and application of this model. The Decision Cell model also allows for a comparative analysis of normative frameworks for health policy. Mechanisms to facilitate adopting a pragmatist approach to rational policy-making are highlighted, as are the potential advantages and challenges of doing so.