Consider the laudable, but now somewhat tarnished initiative to establish evidence-based policymaking. What went wrong? All too often, objective evidence was taken to be data uncontaminated by the bias of a prior theory. But without "the very soul" of a theory as guidance, what constitutes evidence? Objectivity isn't to do with with stripping out all presuppositions. Indeed, the more that's considered possible or desirable, the greater the undetected, uncriticized presuppositions and the less the objectivity. At worst, a desired but unstated goal can be smuggled in at the outset. And the upshot? This well-meant approach is often justifiably derided as "policy-based evidence-making".
Helena Cronin: In the beginning is the theory
I Brockman (red.), This explains everything, s. 157