# Amartya Sen's The Idea of Justice explained: how to compare real alternatives

> Amartya Sen's The Idea of Justice (2009) argues that a theory of justice should help us choose between the real options in front of us. Sen sets aside the search for a perfectly just society, which he calls transcendental institutionalism, and proposes realisation-focused comparison: look at how people actually live, rank feasible alternatives, and remove the injustices we can remedy. Public reasoning open to outside views does the ranking. For radical centrism the book supplies a method: judge each reform against the real alternatives, by its effect on people's lives.

- URL: https://www.radicalcentre.eu/en/articles/amartya-sen-the-idea-of-justice-explained
- Language: en
- Publisher: radical centre / centro radical
- Published: 2026-10-10
- Topic: Ideas & history
- Author: radical centre
- Licence: CC BY 4.0

## Key points

- The Idea of Justice (2009) is Amartya Sen's critique and revision of John Rawls, dedicated to Rawls's memory.
- Sen calls the search for perfectly just institutions transcendental institutionalism and proposes realisation-focused comparison instead.
- Knowing the ideal is unnecessary for ranking two real options: you can compare Kilimanjaro and McKinley without knowing Everest.
- Sen judges outcomes by capabilities, the real freedoms people have to be and do what they have reason to value.
- Public reasoning, open to the views of outsiders, does the ranking; democracy is government by discussion.

Amartya Sen, the Indian economist and philosopher who won the 1998 Nobel Prize in economics for his work on social choice, published *The Idea of Justice* in 2009, with Allen Lane in London and Harvard's Belknap Press in the United States. It is a long book with a simple practical question at its centre. How do we make the world less unjust, starting from where we are? Sen dedicated it to the memory of John Rawls, the philosopher whose work it sets out to revise.

The book matters to radical centrism because it turns the question of justice into a method for choosing between real options. That is exactly what a politics of synthesis needs.

## Two ways of thinking about justice

Sen divides the history of political philosophy into two families. The first, which runs from Hobbes, Locke, Rousseau and Kant to Rawls and Nozick, looks for the principles of a perfectly just society and then designs the institutions that would embody them. Sen calls it transcendental institutionalism. The second family compares the ways people actually live under different arrangements and asks which changes would make things better. Sen counts Adam Smith, Condorcet, Bentham, Mary Wollstonecraft, Marx and John Stuart Mill in this camp, and places himself there too. He calls it realisation-focused comparison.

His objection to the first family has two parts, as Charles Barclay Roger sets out in his review for openDemocracy. The first is feasibility. Reasonable, impartial people may never agree on one single set of perfect principles. The second is redundancy. Even if we had a picture of the perfectly just society, it would tell us little about how to rank the imperfect options we actually face. Sen's illustrations stay with you. Knowing that Everest is the highest mountain in the world adds nothing when you are comparing the heights of Kilimanjaro and McKinley. Believing the Mona Lisa is the greatest painting does not settle whether a Picasso beats a Van Gogh.

So the ideal is unnecessary for comparison, and on its own it is insufficient for it. The work of justice happens in the comparisons.

## Three children and a flute

The book's best-known example shows why one perfect answer is elusive. Three children argue over a flute. The first says it should go to her because she plays it best. The second says he is the poorest of the three. The third says she made it herself, unaided. Each claim rests on a different principle: the good that comes from use, economic equity, and entitlement to what one has made. Each can be defended impartially. A utilitarian, an egalitarian and a libertarian would each hand the flute to a different child, and none of them would be unreasonable.

Sen draws a sober conclusion. Several impartial reasons can survive scrutiny at the same time. A theory that pretends there is only one will end up arbitrary. A practical approach accepts that we will sometimes have only partial rankings, and acts on the comparisons people can agree on, which are often more than enough. Most people agree that a famine, a child out of school or a person denied medical care for lack of money is worse than the alternative, whatever their full theory of the good society.

## Capabilities: what we compare

Comparisons need a measure. Sen's is the capability approach, which he developed over decades and restates in the book. Functionings are the things a person manages to be and do: being well nourished, being educated, getting around. Capabilities are the real freedoms to achieve them, what the Stanford Encyclopedia of Philosophy describes as opportunities cleared of obstacles. Sen defines them as the freedom to achieve what people have reason to value.

The key insight is that equal resources do not produce equal freedom. People convert money and goods into a decent life at very different rates, depending on their health, their surroundings and the social rules around them. A bicycle gives far more mobility to a skilled rider in a city with cycle lanes than to someone who never learnt or who lives beside a motorway. A disabled person needs more resources to reach the same mobility. So Sen asks what people can actually do, and he refuses to fix a canonical list of capabilities in advance. Communities should decide what counts through public discussion.

## Reasoning in public, with outsiders

That brings in the book's last big idea. Rawls imagined principles chosen behind a veil of ignorance by members of one society. Sen calls this closed impartiality: it removes self-interest, but it never tests a society's values against the eyes of outsiders. He prefers Adam Smith's impartial spectator, an imagined observer who can come from anywhere, near or far. Judgements that survive scrutiny from every direction have a stronger claim to objectivity. Democracy, on this view, is government by discussion, and its value lies in public reasoning far more than in the count on election day.

*The Economist* called the book a commanding summation of Sen's work, and it has its critics. Laura Valentini, writing in *Economics and Philosophy* in 2011, argued that Sen misreads Rawls in places and that the Rawlsian approach already does much of what he wants. The debate is worth reading, and we return to it in a separate piece on Sen and Rawls.

## What a radical centre takes from Sen

Sen's method fits the synthesis rule closely. From the left comes his insistence that justice is judged by the lives people can actually lead, so that remediable deprivation, hunger, illiteracy, illness without care, is an emergency to act on now. From the liberal tradition comes his view that freedom of choice sits at the heart of well-being, and his scepticism about grand designs for the perfect society. And from neither comes the idea that holds the book together: we can act on partial rankings, reached in public and open to outsiders, without first agreeing on the ideal.

Put together, that becomes a working rule for policy in Spain and across Europe. Take the problem. List the alternatives that are actually feasible, including doing nothing. Compare what each one does to people's real freedoms, using evidence. Pick the best available option, whichever tradition it comes from, and check the result afterwards. The rest of today's articles apply that rule: to Rawls, to Spain's minimum income and to the way governments write new laws.

## FAQ

### What is the main argument of Amartya Sen's The Idea of Justice?

That political philosophy should help us decide how to reduce injustice by comparing the real alternatives available, instead of first defining a perfectly just society. Sen calls his method realisation-focused comparison.

### What is transcendental institutionalism?

Sen's name for the tradition, from Hobbes and Kant to Rawls, that seeks the principles and institutions of a perfectly just society. Sen argues it is neither necessary nor sufficient for ranking the imperfect options we actually face.

### Why does The Idea of Justice matter for radical centrism?

It gives the radical centre a working method: take the problem, list the feasible alternatives, compare their effects on people's real freedoms, and choose the best available one, whatever tradition it comes from.

## Sources

- [Amartya Sen and the idea of justice](https://www.opendemocracy.net/en/amartya-sen-and-idea-of-justice/), openDemocracy (2010)
- [The Idea of Justice](https://www.penguin.com.au/books/the-idea-of-justice-9780141037851), Penguin (2010)
- [The Capability Approach](https://plato.stanford.edu/entries/capability-approach/), Stanford Encyclopedia of Philosophy (2025)
- [The Idea of Justice](https://en.wikipedia.org/wiki/The_Idea_of_Justice), Wikipedia (2025)