Complexity, 'practical rationality' and evidence-based policy making

Recent work on complexity theory has significant implications for our conceptions of the nature of social systems and for ideas about how we can gain an understanding of such systems and achieve beneficial change. This article seeks to identify some of the key implications for our thinking about the role of evidence in policy making in complex, dynamic social systems. It is argued that recent work on complexity has important implications for approaches. to understanding how social systems work and for ideas about how the course of change in such systems can be influenced by policy action. Processes of 'reflexive social learning' become central to achieving rational guidance of social change but contemporary thinking about evidence-based policy making is underpinned by an 'instrumental rationality' that excludes ethical and moral concerns from rational consideration. However, an important dimension of increasing social complexity involves moral ambiguity and it is argued that normative concerns must be embraced within 'practical rationality' in order to achieve a sound basis for efforts at social improvement.