In this paper, I put forward an argument that sustainability science can make objectively grounded normative claims about what courses of action society should pursue in order to achieve sustainability. From a survey of the philosophy of science, social theory and sustainability science literature, I put forward an approach to justifying these normative arguments. This approach builds on the insight that social theories are value-laden and that dominant and pervasive social practices find their justification in some social theory. The approach: (i) focuses on the analysis of concrete cases; (ii) paying attention to the social practices that produce environmental problems and the theories that support those practices; (iii) examines alternative theories, and (iv) justifies a normative position by identifying the most comprehensive theoretical understanding of the particular case. Although the approach focuses on the analysis of particular cases it does not rely on value relativism. Furthermore, while the focus is on the role of science in producing normative arguments about society’s trajectory, it maintains space for the inclusion of the values of the public in environmental decision-making. However, while this approach aims to provide a rational basis to normative positions, it does not presume that this will lead to social consensus on these issues.