This article considers lay participation in modelling as part of a much larger trend – the inclusion of non-expert publics in areas of environmental decision-making that have traditionally been the domain of those with specialist expertise. The authors note that in the natural and managerial sciences, participatory practices and the inclusion of non-expert publics in ‘expert’ policy domains such as the environment are often portrayed with considerable optimism, especially if they are viewed as potentially able to lead to better decision-making. In the social and political sciences, on the other hand, such participatory practices have often been characterised as intensely disillusioning. The article explores the reasons for these different appraisals of participation. It reports, in particular, upon studies carried out in the social sciences that have analysed and critiqued recent participatory trends, aiming to make these critiques open for debate within the modelling community. The second half of the article documents the creation of a new forum, the Loweswater Care Project (LCP), which has used such critiques to guide its ways of approaching the practice of participation. The paper thus provides an empirical case study, showing what might be gained by basing the practice of participation upon critical social science theory.