Frontiers of Justice is Martha Nussbaum’s most recent contribution to an already extensive body of work on an approach to issues of justice known as “the capabilities approach.” The capabilities approach argues that questions of justice should be settled not by looking at the commodities that people possess, but rather at “what people are actually able to do and to be” (70). Justice requires more than giving people an equal amount of goods; it requires giving people equal capabilities to function in certain key human ways and asking what people need to live lives that are “worthy of the dignity of the human being” (70). Nussbaum argues that the basic requirements of a life with dignity are universal: in order to live “truly human” or dignified lives, all human beings need to have certain capabilities to function guaranteed. To the extent that governments or societies fail to guarantee for their members a threshold level of capability to function in certain basic areas, such governments and societies are unjust.
This book is not simply another reiteration of the capabilities approach; it contains much that is new and interesting. Its central aim is to show how the capabilities approach is able to solve (or at least address) three problems of justice that social contract theories, which are in Nussbaum’s view “probably the strongest theories of justice we have” (3), cannot; it is both a critique of social contract theories and an expansion of the capabilities approach. The three problems concern the extension of justice to people with physical or mental impairments, to all world citizens, and to non-human animals. Nussbaum’s critique of the social contract tradition with respect to these problems is penetrating. She shows that the key assumptions of contractarian theories are highly exclusive: they assume that parties to the contract are rational and equal in power, capacities, and resources; that those who make the contracts are the subjects of justice; and that the purpose of cooperative society is mutual advantage. On any such account, disabled persons and non-human animals are not the subjects of justice. The argument that global justice amounts to a second-stage contract between self-sufficient states roughly equal in power and resources is also highly exclusive, since contemporary states are grossly unequal in these respects and almost never self-sufficient.