First, a warning: this is probably not your ideal summer beach read. Amartya Sen's prose is dense and technical, as one might expect of a Nobel prize-winning economist. If you have trouble with sentences such as: "the perspective of social realisations is a great deal more inclusive than the narrow characterisation of states of affairs seen as culmination outcomes", you may wish to turn straight to the York notes.

The Idea of Justice is, however, a must-read for those who wish to follow the latest developments in leftwing thought. Sen has become the philosopher-economist of choice for the new wave of Labour politicians as they set about rebuilding the party in the wake of the Third Way. His "capabilities approach", developed in previous publications but outlined at length here, illuminates some of the shortcomings of the New Labour project and points towards a more nuanced understanding of how best to tackle deprivation. In this view, raising incomes is of secondary importance; what really matters is increasing the "capability" people have to achieve their goals in life. A person's "capability" may be impaired not only by poverty but also by disability, discrimination or illiteracy, for example.

The same concern for the "kind of lives that people can actually lead" is Sen's starting point for The Idea of Justice. Mainstream political philosophy, espoused by John Rawls and Robert Nozick, among others, has become entirely preoccupied with identifying the characteristics of a perfectly just society: what such a society would look like and which institutions would govern it. In its obsession with such "transcendental" concerns, Sen argues, it has neglected the pressing question of how to advance justice in the kind of flawed, real societies we all live in. "When people across the world agitate to get more global justice they are not agitating for a 'perfectly just' world society, but merely for the elimination of some outrageously unjust arrangements."

Sen situates himself in a tradition of thinkers who have pressed for radical change: Mary Wollstonecraft, Karl Marx, John Stuart Mill. The Idea of Justice is a theoretical work that is unlikely to inspire any real-life revolutions ("down with transcendental institutionalism!" anyone?) but if human-centred politics is the future, then sign me up.