This thesis is motivated by the puzzle that while the practice of collective security continues to grow and expand with more and bigger peacekeeping operations, the system is struggling increasingly to address the threats and stabilize the global world. Thus to find out more about the justificatory background of the reinvention of collective security after the end of the Cold War, an in-depth critical analysis is conducted of the UN Protection Force (UNPROFOR) for the former Yugoslavia and the subsequent peacebuilding missions. Question are asked about whether in fact the problems of multidimensional peacekeeping are limited to bureaucratic and technical flaws that can be corrected through institutional and instrumental adjustments, or if they also relate to more fundamental normative problems of collective security in a global world. As such, the thesis has two main trajectories: collective human security and multidimensional peacekeeping. On the one hand, it addresses the relationship between security and world order, and on the other, the correlation between peace and collective security. By bringing security and peace studies together within a critical analytical framework that aims to inform theory through practice, divides between the discourse and the system of collective security are highlighted and connected with the practical problems of multidimensional peacekeeping and collective security in a global world. Three main sets of findings are made that indicate that multidimensional peacekeeping amounts to an institutionalization of internal conflicts that requires a practice of peace-as-global-governance that the UN is neither technically let alone normatively equipped to carry out. First, the policies of multidimensional peacekeeping have perverse consequences in practice whereby peacekeeping comes at the expense of peacebuilding. Second, in order to terminate multidimensional peacekeeping successfully, the UN is forced to compromise the initial aims of the operations to accommodate practice. Third, the aim of multidimensional peacekeeping is in the doing or in the ritual, rather than in the end result. Against this background, the argument is made that there are conceptual incoherencies between the practice and the system of collective security, which assumes that collective security is a sphere of influence in its own right that can tackle delicate normative dilemmas, both making and enforcing decisions about which processes and needs should be upheld and satisfied at the cost of others.