States have long been understood to have an obligation to protect the international legal rights and interests of others, consistent with the maxim sic utere tuo ut alienum non laedas (use what is yours in such a manner as not to injure that of another). As the world's population becomes more interdependent, this no harm obligation becomes more significant. Further, as knowledge increases about the consequences of human activity for the climate and the environment, the no harm obligation takes on greater relevance vis-à-vis the interests of the Earth's future populations. Future generations’ legal interests have been recognized in the context of sustainable development and through the principle of intergenerational equity. The no harm rule requires that these interests be properly considered and addressed appropriately, commensurate with what is at stake. At a minimum, this may require avoidance of ‘manifestly excessive adverse impacts’.

Administrative decisions are unlawful if they are unreasonable, in the sense that Associated Provincial Picture Houses Ltd. v Wednesbury Corporation made famous. What is Wednesbury unreasonableness, precisely? Courts have not clearly said, and existing academic answers are flawed. Here I propose a new answer. My claim, roughly, is that a Wednesbury unreasonable decision is one that a court is entitled, given the evidence before it, to conclude was wrong, given the evidence before the authority when it made the decision. In a slogan: Wednesbury unreasonableness is demonstrable wrongness.

Proponents of political liberalism standardly assume that the citizens of an ideal liberal society would be overwhelmingly reasonable. I argue that this assumption violates political liberalism's own constraints of realism—constraints that are necessary to frame the central problem that political liberalism aims to solve, that is, the problem of reasonable pluralism. To be consistent with these constraints, political liberalism must recognize that, as with reasonable pluralism, widespread support for unreasonable moral and political views is an inevitable feature of any liberal society. I call this the fact of unreasonable pluralism. This fact threatens Rawlsian political liberalism's account of stability because an overlapping consensus cannot stably order a society pervaded by unreasonable views. My argument also raises questions about the coherence of Rawls's conception of ideal theory.