Our point of analytical departure is that the state of the global environment is deteriorating despite the accumulating body of international environmental law. By drawing on the recent Earth system science concept of interlinked planetary boundaries, this article makes a case for a goal-oriented, purposive system of multilateral environmental agreements. The notion of ‘goal’ is used here to mean a single, legally binding, superior norm – agrundnorm – that gives all international regimes and organizations a shared purpose to which their specific objectives must contribute. A bird’s eye view of the international environmental law system reveals how the absence of a unifying goal has created a condition that is conducive to environmental problem shifting rather than problem solving. We argue that a clearly agreed goal would provide the legal system with a point of reference for legal reasoning and interpretation, thereby enhancing institutional coherence across Earth’s subsystems. To this end, this article concludes by observing that the protection of the integrity of Earth’s life-support system has emerged as a common denominator among international environmental law instruments. Accordingly, we suggest that this notion is a strong candidate for the overarching goal of international environmental law.