Much of the early academic debate in this field was driven by an expanding understanding of policy knowledge and its functions in the policy process. Initially, the focus was limited to concrete or technical knowledge and its role in improving policy choices. This type of instrumental use of policy information has sometimes been called the ‘engineering model’ (Knorr
1977). Research in this tradition soon faced a major paradox. While an ever-increasing amount of policy-relevant information was produced and disseminated, studies of knowledge use almost equivocally attest to the fact that little of this knowledge ever enters the decision-making realm. In light of these disconcerting results, a competing interpretation of research findings emerged that challenged the conceptual premises of the debate. The perceived gap between knowledge production and utilization came to be seen partially as an artifact of the exceedingly narrow understanding of knowledge use that dominated much of the early studies in this field of research (Caplan
1979: 468; Pelz
1978). The distinction between concrete and conceptual knowledge use was introduced to underline that early research was struggling with this multifaceted role of knowledge in the policy process (Weiss
1977a; Rich
1977). This research emphasized that there are more ways in which knowledge can influence policy choices than by producing reliable empirical predictions about the relationship between preconceived means and ends. Weiss (
1977b) claimed that knowledge can inform policy making also by challenging the underlying assumptions and analytical concepts that structure policy choices. Her enlightenment model highlights how information can enter the policy process in ways that alter the decision makers’ fundamental understanding of the issues at stake. Policy knowledge, according to Weiss (
1999: 146), supplies decision makers with the ‘background of ideas, concepts and information that increased their understanding of the policy terrain.’ From this perspective, the primary function of information in the policy process is seen as providing ‘insights into the nature of social problems’ (Weiss
1995: 141). As a result, researchers also began to operate with a much broader definition of policy knowledge. Weiss’ (
1986: 279) use of the term, for example, encompasses ‘research, analysis, evaluation, data.’ Most of the more recent contributions have similarly opted for such a broader definition of policy knowledge. Radaelli (
1995: 162–63), in one of the classic articles on the issue, acknowledges the role of ‘hard’ policy information defined as scientific knowledge, but argues that this type only constitutes one end of a continuum. At the same time, the enlightenment model also established a new understanding of the process through which knowledge influences policy choices. While previous research on instrumental knowledge use was associated with expectations of direct and immediate effects of available information on policy choices, the enlightenment model describes policy dynamics that work ‘in the long term’ (Weiss et al.
2005: 14). ‘Perhaps it takes 5 or 10 years or more before decision makers respond to the accumulation of consistent evidence,’ Weiss (
1993: 98) argues. One reason for this was that conceptual knowledge use was seen as much more diffuse and indirect. To capture the long-term effects of information on the policy process, Weiss (
1980,
1982,
1986) introduced the term ‘knowledge creep.’ According to Weiss, new information and ideas ‘seep into people’s consciousness and alter the way that issues are framed and alternatives designed’ (
1999: 471). Knowledge creep therefore describes a ‘slow trickle’ that produces ‘slow results’ (Weiss
1999: 472).
Several decades after its initial formulation, the enlightenment model has established itself as one of the dominant research perspectives in studies of knowledge use. It has been assessed to capture ‘the most important effect that research and evaluation have had on policy’ (Weiss et al.
2005: 14). At the same time, the model remains insufficiently theorized in key respects. Weiss (
1986: 278) herself notes that the concept of knowledge creep is a largely descriptive metaphor and that little is known about the mechanisms and conditions under which information produces enlightenment effects. While students of knowledge use have grown increasingly impatient with a field of study that is ‘generally silent on the range of underlying mechanisms’ (Mark and Henry
2004: 37), few successful attempts have been made to address these shortcomings (Weiss et al.
2005: 26–27). Arguably the most prominent theoretical elaboration of the enlightenment model in the context of policy research can be found in the work of Paul Sabatier on policy learning. Sabatier developed his well-known framework as an attempt to build directly on the enlightenment model and integrate it into theories of policy learning (Sabatier
1988: 158;
1987: 649; Sabatier and Jenkins-Smith
1988: 124). Yet in terms of its contribution to knowledge research, Sabatier’s work stands out as conservative. In contrast to the enlightenment model, Sabatier’s main interest lies with the role of technical knowledge in the policy process (e.g., Sabatier
1997: 4). Partially as a result of his more limited focus, he finds that knowledge interventions are most likely to affect policy choices if decision-making power is delegated to apolitical expert arenas, and when the issues under consideration allow for straightforward scientific appraisal (Sabatier
1997: 4,
1988: 159). Knowledge effects are seen as primarily affecting secondary aspects of policy formulation, such as instrument choice and implementation strategies. Changes at the level of the underlying perception of problem structures, on the other hand, are largely shielded from evidentiary influence. Unsurprisingly, critics have charged that his theory of policy learning departs substantially from key interests of the enlightenment model that was its original point of departure (e.g., James and Jorgensen
2009; Fischer
2003; Bennett and Howlett
1992).
With the outlined shift from instrumental to conceptual use, knowledge research has overcome a rationalist bias that characterized the early work in this field, but it has also remained limited in several respects. Founded on a largely implicit notion of policy learning, the use of conceptual knowledge has become closely associated with a single type of knowledge effect that is described as diffuse, indirect and difficult to observe. Even more importantly, research in the enlightenment tradition also remains solidly focused on the substantive dimension of knowledge use. It largely ignores the question of how the influx of knowledge about the nature and structure of policy problems affects the political process beyond informing the search for suitable policy solutions. The next section will argue that conceptual knowledge also has a political function in the policy process that much of the existing literature fails to address. As a result, central mechanisms of knowledge transfer and corresponding knowledge effects in the policy process have remained underexplored.