We make a case in this article for re-orienting public health, based on evidence that societies across the globe are now facing inevitable change for which public health remains insufficiently prepared. We focus on the relationship between different sustainability ideals, displayed through rhetoric and discourse and the reality of a number of challenges in the 'modern' world. We briefly describe discernible elements of public and policy rhetoric around sustainability, as an important background for public health efforts, and present two significant public health discourses. We then outline some of the challenges to sustainability; some relate to the powerful social systems and cultural values associated with modernity, while others refer to broader environmental issues. These are not unconnected. We conclude by outlining the possibilities for sustainability, which include a transition to a more sustainable form of society that could lessen global inequalities, combat emerging problems, such as obesity, depression and addictive behaviours, and improve individual and social levels of well-being. We believe that this may well require a change of consciousness for a change of age, so the scope and scale of the required response should not be underestimated.