The post-normal science of precaution

Science now finds itself in a new and troubled situation. The traditional optimistic picture is problematic and compromised at every turn. The scientific system now faces a crisis of confidence, of legitimacy and ultimately of power. We can usefully distinguish two sorts of science. The 'mainstream' is reductionist in style, and increasingly linked to industry. By contrast, the 'post-normal' approach embodies the precautionary principle. It depends on public debate, and involves an essential role for the 'extended peer community'. It is based on the recent recognition of the influence of values on all research, even including the basic statistical tests of significance. It is the appropriate methodology when either systems uncertainties or decision stakes are high; under those conditions the puzzle-solving approach of 'normal science' is obsolete. This is a drastic cultural change for science, which many scientists will difficult to accept. But there is no turning back; we can understand post-normal science as the extension of democracy appropriate to the conditions of our age. (C) 2003 Elsevier Ltd. All rights reserved.