
She argues that a just society must ask not only who has how much, but what people can actually do and be.
Nussbaum trained as a classicist and philosopher simultaneously and has never quite stopped being both. Her central contribution is the capabilities approach, developed alongside the economist Amartya Sen: instead of measuring welfare by income or preference-satisfaction, ask what people are actually able to do and be. Her list of central human capabilities — life, health, bodily integrity, sense and imagination, emotion, practical reason, affiliation, living with other species, play, and control over one's environment — provides a floor below which no just society should allow people to fall. She has applied this to gender, disability, and sexual orientation, and devoted a parallel career to the emotions, arguing that feelings are not noise in the moral life but forms of intelligent evaluative response. She has written on grief, anger, compassion, and especially disgust — which she thinks does more damage in public life than almost any other emotion.

“Emotions are not just the fuel that powers the psychological mechanism of a reasoning creature, they are parts, highly complex and messy parts, of this creature's reasoning itself.”
Nussbaum joined the University of Chicago Law School in 1995 as Ernst Freund Distinguished Service Professor. The appointment — a philosopher in a law school — reflected her commitment to philosophy as a practical discipline. She had been developing the capabilities approach with Amartya Sen, arguing that justice requires enabling people to actually do and be what matters.
Nussbaum developed the capabilities approach partly as an answer to Rawls: his account of primary goods was too thin and too focused on resources, missing what people actually need to live fully human lives.