Sustainability as described in Agenda 21 is characterised by a complex system of interacting targets in four dimensions social, environmental, economic and institutional. This four-dimensional approach is illustrated with a new communicative tool based on a spherical structure, the "prism of sustainability". In the economic debate, these dimensions of sustainability are well known; they are referred to as production factors, or as four types of capital (man-made, natural, human and social capital) that have to be serviced with reinvestments from the surplus generated. From a system dynamics point of view, they can be considered to be independent but coupled non-linear self-organising systems. Sustainability refers to the conditions for maintaining their self-organisation processes, and investment to the measures that can be taken to strengthen the resilience and viability of the systems. Consequently, the "currency" of investment cannot be money in all cases, but has to correspond to the system characteristics. In this context, the question of weak or strong sustainability based on substitution possibilities turns out to be more of a methodological artefact of economics, resulting from single factor analysis instead of a multi-criteria approach necessary for sustainable development. This paper focuses on the environmental and the institutional dimension, i.e. on the natural and social capital. For the environmental dimension, the reduction of material flows and the need for safeguarding biodiversity are key targets, for the institutional dimension, it is time management, harmonising social rhythms and the creation of "chronotopes".
