In deciding on what actions to take, the policy maker is confined to choose among a certain set of policy-tools. These tools are aiming at, through the manipulation of certain independent variables, achieving the occurrence of a desired dependent variable. Variables that fall outside the range of possible manipulation through the existing kit of policy-tools thus appear as irrelevant. It is therefore the position, and the corresponding kit of policy-tools, that determine what it is possible to manipulate through policy, and hence determine what constitute relevant knowledge. This has direct political implications.
Policy is the enactment of politics.
It is a form of politics that claims legitimacy from being portrayed as the technical implementation of a rational solution to a problem. Scientific knowledge in this sense performs a symbolic task as it legitimizes and renders credible that is, rational and efficient political action. When a political actor is able to support his actions or opinions with reference to some body of scientific knowledge or facts, it becomes difficult to argue that they are untenable or inappropriate. As the main conveyer of authoritative reality , science embeds a substantial form of power in political life. The concrete manifestations of these processes will differ depending on the field of intervention.