The notion of sustainable development is highly controversial – a fact which appears thoroughly appropriate given the fundamental societal relevance of the questions involved. However, sustainability conflicts do not always imply a fruitful debate. The way in which such conflicts are addressed and handled quite often proves to be problematic: for example if sustainability goals are said to be incompatible while there is no evidence for their incompatibility, or if action is blocked because upcoming decisions are presented as being not open to serious arguments.

The present study aims at contributing to a better understanding of problematic sustainability conflicts and thus to successful sustainability-oriented action. It comprises a conceptual analysis of sustainability assessments with special attention to the integrative concept of sustainable development, one of the most recent approaches to operationalize the general principle. The focus is on conflicting sustainability goals as the most important form of addressing sustainability conflicts in the scientific context. Special emphasis is put on a question that has so far been ignored in the existing studies on the theory of sustainable development, a question which also proves to play a crucial role for solving the problem of goal conflicts: should sustainability norms be conceived as principles (which can be balanced or weighed) or as rules (which cannot). Beyond this focus as regards content, the present study aims at bridging the gap between theoretical and practical work on the concept of sustainable development.

The most important result of the study is that the general principle of sustainable development shall not be operationalized with principles, but with rules. The fact that this result is a polar opposite to the common intuition can be explained by a concatenation of misconceptions originating mostly from an ambiguous terminology. The problem of handling goal conflicts, which nevertheless arises during sustainability assessments, cannot be solved by using weighing methods, but in a fundamentally different way, namely by using a scenario-based assessment method. Such a five-step method is being developed at the end of the study.