Education for sustainable development (ESD) raises critical questionsregarding what knowledge should be taught and what the learning outcomes should be. The aim of this thesis is to explore epistemological, ethical, and critical dimensions of ESD. There are two empirical sites. One is a transdisciplinary educational project with upper-secondary Swedish students (n=208) from 16 different schools; the other involves teachers (n=158) at a large Swedish upper-secondary school implementing ESD.The research design is emergent, combining empirical and theoretical studies. A questionnaire instrument to explore students' epistemic beliefs (personal theories of knowledge and knowing) was constructed. Exploratory factor analysis identified five dimensions: transdisciplinary, certain, quick, collaborative, and simple knowledge. These showed predictive power in a multiple regression analysis. Another instrument was constructed to examine teachers' ESD competences. Four dimensions were identified.Wicked sustainability challenges require the individual, education, and society to adopt new ways of thinking, learning, and acting. Calls for transformation, supported by supranational organizations, have contributed to an increased focus globally on competence-oriented knowledge in the curriculum. Ethical competence, action readiness, and normative competence are nested concepts explored theoretically in this thesis. Philosophizing with is a central method, which invites epistemology as a voice into the analysis. Transdisciplinary and pluralistic ESD allow for ethical issues to surface in the classroom. It is theorized that an ESD teacher needs to be both morally Preface When I first began to work as a teacher in upper-secondary school, there were five lecturers, holding doctorate degrees, in physics, mathematics, technology, Swedish and English, at my school. I was inspired by them and started as a "shadow" PhD-student in English literature without funding. For a few years I tried to combine full-time teaching with research studies, but in the end I had to choose. Many years later, falling back on a long teaching experience of English and Swedish, an opportunity of funding from a governmental grant (Kammarkollegiet) emerged, and I was able to accept a position as a PhDstudent at the Centre for Educational Sciences and Teacher Education [CUL, Centrum för utbildningsvetenskap och lärarforskning] in Gothenburg. I got a licentiate degree in pedagogical work in 2014, and now, this second leg of research studies, towards a doctorate degree, the municipality of Uddevalla has kindly made it possible for me to study half-time, teaching half-time. Special thanks to my headmaster Tomas Ländström for being instrumental in making this professional development possible, and thanks to Stefan Einarsson, head of Uddevalla gymnasieskola, for investing in this knowledge project, endorsed by the local educational administration of Uddevalla municipality. Thank you! I wish to express deep gratitude to my two supervisors Professor Olof Franck and Associ...