A well-known definition of planning is that proposed by Friedmann (1993), who called it “a professional practice that specifically seeks to connect forms of knowledge with forms of action in the public domain” (p. 482). So planning thought must focus on the relationship between research and design, on the knowledge-action nexus. How is this nexus achieved? What are the methodological pitfalls involved? This work is about how the nexus has been conceptualised by Dutch planning.