Post-Normal Science and the complexity of transitions towards sustainability

The theory of Post-Normal Science is now approaching obsolescence; it needs to be renewed and enriched. In historical perspective, PNS evolved from a criticism of Probabilistic Risk Analysis, and put the essentially political idea of Extended Peer Community at its core. Establishing the legitimacy of the EPC requires a review of the methodology of science in the policy process. The time is not ripe for a modification of PNS, and so the best move for-ward is to raise the issue of Sustainability. For that I sketch a theory of complex systems, with special attention to pathologies and failures. That provides the foundation for a use of 'contradiction' as a problem incapable of resolution in its own terms, and also of 'characteristic contradiction' that drives a system to a crisis. With those materials it is possible to state the characteristic contradiction of our modern industrial civilisation, and provide a diagrarri with heuristic power. (c) 2007 Elsevier B.V. All rights reserved.