The idea of "sustainability" as a core value has slowly permeated policy and practice at governmental and institutional levels, in public and private policy. However, at times when social and economic crises have revealed the fragility of existing institutions and policies, it is important to consider how sustainability is -- and could be -- integrated into educational policies. In this theoretical contribution to a special issue on "Societal sustainability", the authors draw on available literature and knowledge. They begin their paper by summarising the conditions under which the concept of "sustainability" entered political discourse in the early 1970s and outline how it has influenced educational research. They then introduce the longstanding debate about the relative role of tradition (in terms of traditional cultural and social order) and change (in terms of efforts to provide learning opportunities for everyone) in adult education. Finally, they argue for a rethinking of the ontology of sustainability: this, they suggest, can shed new light on its relationships with adult education and learning and social justice. [This article draws and further elaborates on ideas expressed in Milana, M., Rasmussen, P., & Holford, J. (2014). "Public policy and the "sustainability' of adult education." "Encyclopaideia," 18(40), 3-13. DOI: 10.?6092/?issn.?1825-8670/?4658.]