The fallacy of evidence based policy
  The use of science for policy is at the core of a perfect storm generated by the insurgence of several concurrent crises: of science, of trust, of sustainability. The modern positivistic model of science for policy, known as evidence based policy, is based on dramatic simplifications and compressions of available perceptions of the state of affairs and possible explanations (hypocognition). This model can result in flawed prescriptions. The flaws become more evident when dealing with complex issues characterized by concomitant uncertainties in the normative, descriptive and ethical domains. In this situation evidence-based policy may concur to the fragility of the social system. Science plays an important role in reducing the feeling of vulnerability of humans by projecting a promise of protection against uncertainties. In many applications quantitative science is used to remove uncertainty by transforming it into probability, so that mathematical modelling can play the ritual role of haruspices. This epistemic governance arrangement is today in crisis. The primacy of science to adjudicate political issues must pass through an assessment of the level of maturity and effectiveness of the various disciplines deployed. The solution implies abandoning dreams of prediction, control and optimization obtained by relying on a limited set of simplified narratives to define the problem and moving instead to an open exploration of a broader set of plausible and relevant stories. Evidence based policy has to be replaced by robust policy, where robustness is tested with respect to feasibility (compatibility with processes outside human control); viability (compatibility with processes under human control, in relation to both the economic and technical dimensions), and desirability domain (compatibility with a plurality of normative considerations relevant to a plurality of actors). 
Andrea Saltelli, Mario Giampietro
q-fin.EC physics.soc-ph