This paper was prepared to present at the Farmer First Revisited: 20 Years On conference at IDS, University of Sussex, UK, December 2007. Its focus is the challenge of strengthening agricultural innovation systems. The paper prefaces this discussion by reflecting on an apparent paradox. While agricultural innovation has never been better studied and understood, many of our ideas about innovation have failed to fundamentally change the institutional and policy setting of public and private investment intended to promote innovation for development. The paper asks "students of innovation" why a virtual spiral of innovation practice and policy learning hasn't emerged. The paper then locates the current interest in innovation systems in the evolving and contested approaches to agricultural development, noting that this is characterised by a long history of false dichotomies. The contingencies of the emerging agricultural scenario will demand the more networked modes of collective intelligence and innovation that are embodied in the innovation systems concept. The paper argues, however, that the innovation systems idea should be view as a metaphor for innovation diversity, rather than another competing innovation narrative. The way forward, it is suggested, is to create a united front of different collective intelligence-based innovation narratives to kick-start the virtuous spiral of innovation practice and policy learning. This is needed to strengthen agricultural innovation systems and so achieve developmental goals. The paper argues that it is the responsibly of all us "students of innovation" to argue for this space for diversity to flourish and to help consolidate and promote what is known about agricultural innovation. If we aren't more successful in stimulating institutional and policy change we will still be debating these issues 20 years hence.Agricultural innovation systems, institutional and policy change, space for diversity, innovation narratives, collective intelligence, self-reflection.