Agriculture is facing increasing challenges as a result of climate change, biodiversity loss, environmental degradation, and demographic change. Yet, at the same time, currently dominant agricultural practices contribute to exacerbate these challenges. It is therefore widely recognized that there is a need for an agricultural sustainability transition. However, what this transition should look like and how it should be brought about is a value-based, normative judgement with differing implications for different people, making transition processes inherently political. In order to govern these processes in a way that recognizes the ethical implications of the political nature of agricultural transitions, we need to understand all the components that influence, and are influenced by, transition processes, interactions across societal levels, and the normative and power dynamics that come together to shape the direction and outcomes of transition processes. In addition, we need insights into what aspects people consider when they build their perceptions of the legitimacy and justice of an agricultural transition. In this paper we draw together overarching lessons learned from extensive reviews of dominant transition, legitimacy, and justice theories, interviews with stakeholder organisations, and a survey of 400 English adults.