Literature about public decision making experiences, including stakeholders' engagement, offers best practices but also reports of unsuccessful case studies. Meaningful participation activities require direct integration of stakeholders into all the phases of the public decision process to unleash innovation. Often, policy making incorporates participation late in the process, after the problem definition has occurred, alternatives have been defined, without considering stakeholders' knowledge and problem understanding. The early stage of policy alternatives design is essential to the development of policy. Our research presents an extensive literature review with respect to policy design and design theory in order to show that the formal process of generation of alternatives has been little investigated. There is a demand for methodologies aiming at supporting policy makers and relevant stakeholders during policy design. In this regard, this paper introduces (and explores) the operational role of design theory in the policy making process for the generation of policy alternatives. Design thinking, as a way to inform a collective problem definition leading to innovation, highlights the value of early stakeholders' engagement. The aim of this paper is to understand, from an operational point of view, what "design" means in a policy making context, developing an innovative approach for assisting the formalization of policy design. The paper uses the results of a pilot case study to illustrate the application of the Concepts-Knowledge theory framework to support the innovative design of policy alternatives for the groundwater protection policy of the Apulia Region (southern Italy). Response to Reviewers: Dear Editor, Many thanks for the opportunity granted to further improve the manuscript. We are thankful to the Reviewers for the appreciation of our revisions and we list below our answers to their last suggestions. The section numbers refer to the revised manuscript. The revised text has been highlighted.