This dissertation presents an historical-sociological study of how governments of the modern western state use the language and techniques of quantification in the domain of social policy. The case material has an Australian focus. The thesis argues that by relying on techniques of quantification, governments risk introducing a false legitimacy to their social policy decisions. The thesis takes observed historical phenomena, language and techniques of quantification for signifying the social, and seeks meaningful interpretations in light of the culturally embedded actions of individuals and collective members of Australian bureaucracies. These interpretations are framed by the arguments of a range of scholars on the sociology of mathematics and quantitative technologies. The interpretative framework is in turn grounded in the history and sociology of modernity since the Enlightenment period, with a particular focus on three aspects: the nature and purpose of the administrative bureaucracy, the role of positivism in shaping scientific inquiry and the emergence of a risk consciousness in the late twentieth century. The thesis claim is examined across three case studies, each representative of Australian government action in formulating social policy or providing human services. Key social entities examined include the national census of population, housing needs indicators, welfare program performance and social capital. The analysis of these social statistics reveals a set of recurring characteristics that are shown to reduce their certainty. The analysis provides evidence for a common set of institutional attitudes toward social numbers, essentially that quantification is an objective technical device capable of reducing unstable social entities to stable, reliable significations (numbers). While this appears to strengthen the apparatus of governmentality for developing and implementing state policy, ignoring the many unarticulated and arbitrary judgments that are embedded in social numbers introduces a false legitimacy to these government actions.