This thesis takes its point of departure in the change of emphasis in the field of environmental and sustainability education (ESE) towards the inclusion of social and human development issues. The theoretical frames of the thesis are poststructural and postcolonial theories, from which different writings, central concepts and approaches are drawn. The thesis also builds on a pragmatist and anti-essentialist approach which argues that we socially construct the meaning of right and wrong and what works better in our lives on the current problematic or situation. The results are presented in four studies and the thesis has three purposes. The first purpose is to describe and investigate theoretical perspectives that take a critical stand on and offer alternatives to universal and consensus-oriented approaches. This purpose is the central focus in the first and second studies. The first study examines the re-emergence of classical cosmopolitanism and contemporary views of the perspective with the intent of discussing its potential for the development of education for sustainable development (ESD). The second study aims to clarify the philosophical problem of addressing universally sustainable responsibilities and values in environmental and sustainability education. The second purpose is to investigate teachers’ ethical reflections in a first-hand intercultural experience. This purpose is dealt with in the third study, where seven Swedish upper secondary school teachers facing particular conflicts of interest and moral situations during a study visit to Central America are interviewed. The third purpose is to investigate how teachers deal with the complex issues of intragenerational equity or social justice in their teaching. This is dealt with in the fourth study, which explores how teachers integrate issues of social justice into their teaching of global sustainability. My hope is that this thesis will contribute to the discussion about how teachers can develop a conscious and critically informed approach to the teaching of environmental and sustainability issues and also contribute to theoretical and philosophical discussions about universalism, normativity and global ethics within environmental and sustainability education research.