Around the world, there is a growing interest among policy scholars and practitioners in the role of knowledge in relation to public policy. These debates are accompanied by some confusion about what is meant by knowledge or evidence, as well as controversies around the role of scientists and suspicions of increasingly technocratic decision making. Our aim is to provide a useful overview of the major debates in this paper, and to trace six dominant discourses in current research that address the role of scientific knowledge or expertise in the policy process. We distinguish evidence-based policy making, knowledge utilisation, policy learning, knowledge transfer, social construction of knowledge and boundaries, and knowing in practice as sep...