At least since the publication of Isaiah Berlin's famous essay "Two Concepts of Liberty" nearly half a century ago, political philosophers have argued vigorously over the relative merits of "positive" and "negative" accounts of freedom. Matthew Kramer writes squarely within the negative-liberty tradition, but he incorporates a number of ideas that are quite often associated with theories of positive liberty. Much of The Quality of Freedom is devoted to elaborating the necessary and sufficient conditions for the existence of particular freedoms and unfreedoms; however, the book's cardinal objective is to establish the measurability of each person's overall freedom and of each society's aggregate freedom. On the one hand, Kramer contends that the existence of any particular instance of liberty or unfreedom is a matter of fact that can be confirmed or disconfirmed without any reliance on evaluative or normative considerations. On the other hand, he argues that the extent of each person's overall freedom or unfreedom cannot be ascertained entirely in the absence of evaluative assumptions. By combining those two positions and developing them in detail, Kramer pits himself against all positive accounts of liberty and most negative accounts. In the course of so doing, he aims to demonstrate the rigorous measurability of overall liberty—something that many writers on freedom have casually dismissed as impossible. Although Kramer concentrates principally on constructing a systematic analysis of sociopolitical freedom, he engages critically with the work of many of the leading contemporary writers on the topic.