IB Philosophy 10.6.2 Central Human Capabilities Key Definitions

The conversion problem, central to Nussbaum and Sen's capabilities approach, is the observation that different people convert the same resources into real opportunities at vastly different rates. A person with a disability, an elderly person, or a pregnant woman may need far more resources than an able-bodied adult to achieve equivalent effective freedom.

the principle, central to Martha Nussbaum's capabilities approach, that each capability on the list is qualitatively distinct and cannot be replaced or compensated for by a surplus in another capability. Unlike utilitarian frameworks that allow trade-offs between goods, non-fungibility means that a nation cannot satisfy the demands of justice by producing wealth while neglecting bodily integrity or political participation.

in Nussbaum's capabilities framework, the capability to form a personal conception of the good and to engage in critical reflection about how to plan one's own life. She regards practical reason as one of two architectonic capabilities (alongside affiliation) that organise and give structure to all the others: without the ability to deliberate and choose, the other capabilities cannot be exercised in a fully human way.

Nussbaum's threshold principle holds that justice requires securing every person a minimum level of each central human capability, below which no one should fall, while leaving individuals free to pursue their own conception of a flourishing life above that floor.