The capabilities approach to equality, developed by Amartyr Sen and Martha Nussbaum, seeks to answer the question: what is a proper measure of a person's condition for the purposes of determining what we owe each other, as a matter of justice? While the capabilities theory has avoided many of the conceptual difficulties that have undermined competing accounts of egalitarian justice, recent criticisms have raised questions regarding the focus, structure and justification of the theory. In this volume, leading scholars present new and original essays that address these controversies.