Why perfect policy coherence is unattainable (and may be ill-advised)

Classic studies of 'perfect' policymaking use an ideal-type to identify and reflect on policymaking in the real world. I use this approach to review studies that seek policy coherence, show how policy theory insights help to identify real-world dynamics, and prompt debate on what would constitute perfection. The ideal-type 'perfect policy coherence' initially helps to identify barriers to policymaking integration and the production and delivery of a coherent policy mix. It has the following elements. There is high and consistent attention to a problem, and solving that problem is the highest strategic priority. There are effective means to produce evidence-informed policy and manage competing beliefs and interests. There is a perfect means to coordinate policy implementation. The strategy works as intended. There are clear and agreed measures of success, and meeting targets signals substantive progress. The policy strategy and mix are credible and durable. I use the ideal-type to show that fragmentation and incoherence are inevitable in the real world. I argue that this 'coherence gap' - between ideal-type and real-world policymaking - is not all bad, then compare competing - 'top down' and 'bottom up' - ways to seek integration and coherence.