There are many theories that can inform analysis of how science advice is done or should be done. Here I define “science advice” as “practices involving individuals, organisations and structures that mobilise natural and social scientific and engineering knowledge into public decision-making”. In this seminar, I will demonstrate that although some theories are well elaborated, empirical proof for the described changes, roles and processes in science advice is limited. After outlining a proposed research programme into science advice at local, national and international levels, I will offer a pragmatist analysis (with some Latourian elements) of the Intergovernmental Panel on Climate Change. I will conclude with presenting elements of an ethos of science advice, which are based on experiences with implementing post-normal science at the PBL Netherlands Environmental Assessment Agency.