This thesis is a record of research exploring the limitations to successful policy implementation. Using Community Care as the illustrative example, it asks what these limitations might be, casting a particular light on the part played by care managers, the front-line policy implementers responsible for "needs assessments" which is a key activity in the implementation of Community Care. There is a tension in care management between the influence of procedures and the degree of discretion necessary for needs assessment to be completed effectively. In what ways, then, are policy intentions affected by the activities of care managers? Community Care is an illustration of a public policy imposed by central government through a top-down process of implementation in what is argued as a rationalist endeavour to simplify the complexities of community care and reduce it to questions of technique and structure. This attempt to present a unified conceptualisation of community care is backed by managerial procedures referred to in the public management and policy literature as "managerialism". Social work practice theory provides a third example of the rationalist attempt to simplify processes involving complex social interactions. The limitations to rationalist explanations of community care implementation and the necessity for a different kind of analysis are explored. There is a parallel with the research methodologies employed for this research. The initial interviews were helpful in revealing the degree to which policy implementation was being thwarted by care managers, but this resistance was mirrored in their rejection of my interpretation of their practice. The common thread running through the normative approach to policy implementation, management, social work practice and research methodology is an adherence to positivist forms of knowledge. The implementation of Community Care raises questions of epistemology and ontology that undermine these powerful forms of knowledge. The claim is that a different epistemology suggests practices more likely to lead to effective outcomes. An organisational orientation to effectiveness is revealed in the degree to which outcome has become wedded to techniques of scientific rationalism. A service orientation would define outcome by the degree to which the needs of vulnerable adults were met through reflection upon key relationships. The first of these is an exercise in objectivity which is not well equipped to take account of the subjective experiences of practitioners exploring needs in relationship with vulnerable adults. The service orientation suggests an experiential and participative epistemology in which people engage in the process of learning and understanding most successfully when it is collaborative rather than imposed. The second phase of fieldwork was an experiment using a method built upon a participatory epistemology and gives the reader a glimpse of what might be possible in direct contrast to rationalist approaches. Work with two co-operative inquiry groups has led me to new understandings about the nature of learning for individuals and organisations. The thesis concludes that an effective learning environment facilitating positive and reflective use of discretion can be created through co-operative inquiry, although any approach would need to include other important participants, notably managers and service users, if it is to maximise its effectiveness in the long term.