Sen's capability approach is philosophically rich and deliberately open-ended. It does not specify which capabilities matter or how to weigh them against each other. This is partly a feature, Sen is suspicious of imposing a single list from the outside, and his framework is designed to be responsive to democratic deliberation about what matters in particular contexts. But it is also, critics note, a bug: without some account of which capabilities are essential, the framework has difficulty generating specific policy conclusions or grounds for saying that particular deprivations are unjust regardless of what local deliberation concludes.
Martha Nussbaum (born 1947), philosopher, classicist, and among the most prolific and influential philosophers alive, took Sen's framework and gave it more precise normative teeth. In a series of works culminating in Creating Capabilities (2011), she developed a list of central human capabilities that she argues every person is owed as a matter of basic justice, regardless of their society's particular values or deliberative conclusions.
Nussbaum's list has ten entries:
- Life: being able to live a human life of normal length
- Bodily health: good health, including reproductive health; adequate nourishment; adequate shelter
- Bodily integrity: freedom from assault, including sexual violence; freedom of movement
- Senses, imagination, thought: being able to use the senses, to imagine, to think, to reason, in a truly human way, informed and cultivated by education
- Emotions: being able to have attachments to things and people outside ourselves; not having emotional development blighted by fear or anxiety
- Practical reason: being able to form a conception of the good and engage in critical reflection about one's own life
- Affiliation: being able to live with and toward others; having social bases of self-respect and non-humiliation
- Other species: being able to live with concern for and in relation to other animals, plants, and the world of nature
- Play: being able to laugh, play, and enjoy recreational activities
- Control over one's political and material environment: being able to participate effectively in political choices; holding property on an equal basis with others; having the right to seek employment on an equal basis
Nussbaum argues these capabilities are not derived from a single comprehensive doctrine but are supported by an overlapping consensus across different reasonable traditions, a Rawlsian move that allows the list to function as a cross-cultural basis for human rights without requiring agreement on ultimate metaphysical or religious foundations.
The threshold principle is important: Nussbaum does not claim that a just society maximizes capabilities. She claims that a just society brings every person above a threshold level of each central capability. Below the threshold, a genuine human life is not possible. Above the threshold, societies are free to arrange capabilities differently according to their own values.
The list has been criticized from several directions. Some argue it is too culturally specific, that the emphasis on individual autonomy and practical reason reflects a specifically liberal Western conception of the good life that should not be imposed globally. Others argue it is too thin, that leaving everything above the threshold to democratic deliberation avoids the hard distributional questions. Nussbaum's responses are sophisticated and worth engaging with, but the tensions are real.