This thesis is a philosophical study of New Public Management (NPM). NPM is a theme used within the mainstream public management literature to explain and critically evaluate the changes that occurred within the public sector since the 1990s. In this study, I aim to develop the argument that there is a crisis in the public sector that results from the NPM regime. To develop this argument, I draw upon the Aristotelian philosophy of Alasdair MacIntyre and identify two distinct spheres of the public sector: practices and institutions. I then argue that NPM generates a certain type of conflict between these two spheres of the public sector. This is a conflict that is related, first, to different and rival presuppositions of practices and institutions, regarding the good of human beings, and then, to the power relationships that are introduced to the public sector through new management methods of NPM. These new management methods assert power over the practices through redefining the meaning of quality and good performance in a way that is contrary to the meanings attached to them by the practitioners. Practitioners in turn resist to this process and conflict with the institutions. The conflict turns into a crisis because the conflict can only be resolved, if either the NPM is removed from the public sector or practices cease to exist in the way that MacIntyre understands them.