Just when you thought democratic socialism was buried, a theory of justice based on people not politics

What is justice? One hallowed answer, stretching back to the heyday of Roman law, is that justice is the constant and perpetual will to give to each person what is really due to them: their own, what belongs to them, their property, or, as Americans most naturally say, their rights. So seen, justice is in the first place a virtue: a disposition of the mind to respect in action a set of authoritative rules. It requires above all consistency and impartiality, an indifference to personal or group charms or disfigurations (justice is blind), perhaps also a certain serenity and detachment in face of human importunities, blandishments and menaces. Yet, however consistent and impartial it may be once in action, justice cannot come into play (or fail to do so) without presuming the authority of the set of rules in question, whether these be rules of law, morality, religion, or merely etiquette; and it cannot vindicate its own standing without establishing that these rules themselves deserve the authority they claim: that they are the right rules, and not merely arbitrary products of time, chance, and the brutal whimsicality of power.

When Stuart Hampshire bluntly affirms that Justice is Conflict , he is neither calling into question the virtue of justice nor denying the need to identify (and seek to offset) the impact of force and fraud on the formal and informal rules of human associations. He is simply trying to restore a balance that he sees as tilted too far in one direction, under the pressure of philosophical misconceptions and deep misjudgements of what human (and for that matter animal) life is, or could be, like. But how can he hope to do this by equating justice with (of all things) conflict?

No one doubts that human beings disagree sharply across time and space over what they owe one another, or that their disagreements endlessly inflame their already intense rivalry to get what they want. The depth and intensity of this rivalry, and the bitterness of their bruised sentiments at the ways in which their fellows treat them, are precisely what make justice so vital in the first place. The central strand of recent liberal political philosophy fully accepts the depth of imaginative disagreement, both between and within communities, over what to value. It grounds its commitment to equal opportunity for every human being to choose and live out their own plan of life, aiming at their own conception of the good, on the moral, political and epistemic impertinence of anyone else presuming to tell them what they should live their lives for. It is hard at this level to see how philosophers could go further in acknowledging the depth of imaginative confinement within an individual's own experience, or the heterogeneity and force of the personal commitments that emerge from that confinement. In contrast with Hampshire, however, both John Rawls and Ronald Dworkin could scarcely be further from equating justice with conflict. For all the differences in their intellectual strategies and presumptions, each has set himself to build a theory of awesome scope and pertinacity, which shows as clearly as can be shown just why the heterogeneity of human imagination makes it just to give every human being the chance to shape their lives for themselves. Rawls may have prescinded somewhat from his initial A Theory of Justice in developing Political Liberalism , and done so precisely because he came to take the hazards of domestic political conflict more seriously. Dworkin may have chosen to explore at greater length in his later work the casuistry of especially profound evaluative disagreements (notably in the case of abortion), because he too came to feel the bitterness of moral conflicts in his own society as more of a political threat. But neither has been discernibly tempted to alter their philosophical style or mode of intellectual procedure for the purpose.

When Hampshire chose to give as his Tanner lectures at Harvard University in 1996-97, the talks which became Justice is Conflict , he was picking up a challenge as well as issuing one. Harvard is not merely much the richest university in the world, it has also been Rawls's own university virtually throughout his career as a teacher. Justice is very much a Harvard subject, the topic over the past three decades not simply of Rawls but of many other colleagues responding to him: Robert Nozick, Michael Sandel, Michael Walzer, Judith Shklar, Amartya Sen, Tim Scanlon. If Hampshire did not come exactly to bury any of these offerings, he certainly did not come to praise them.

Hampshire is an imposing figure, tall, elegant, handsome, full of a sense of life lived in a real world far beyond the academy. While he has always moved in the loftiest philosophical circles, ran for some years one of the most admired American philosophy departments, and later headed one of Oxford's grandest colleges, he has also always been somewhat out of style with most of his philosophical contemporaries. He favours the largest of subjects - Thought and Action, Morality and Conflict, Innocence and Experience, Freedom of the Individual - and treats them very much as such, with the effortless fluency of a Renaissance intellectual and a minimum of technical elaboration.

Justice is Conflict is a very short book on a great many weighty topics. It is easy to see some of the challenges that it chooses to take up; but what exactly is the challenge that it issues? Summarising crassly, I think it is the challenge to recapture the sense of justice and its overwhelming human importance from increasingly scholastic unreality and restore to it a combination of sociological, psychological and political realism. To do this, Hampshire argues: "We need to turn around the mirror of theory, so that we see ourselves both as we are and as we have been." Hampshire's title is taken from a characteristically terse and enigmatic dictum of Heraclitus, the most flamboyant and disturbing of the pre-Socratics. Like Heraclitus, Hampshire assimilates justice to strife rather than serenity because he sees strife as permeating life. To live is to struggle. This is certainly a very different image from the steadily risk-reducing Rawlsian chooser behind the veil of ignorance. It accepts the ineliminability, permanence and propriety of strife within every individual human being, as much as in all relations between individuals, groups, communities and states. Struggle is always dangerous, and its outcomes are sometimes ghastly. But to be alive at all is to be at risk. The only place beyond risk is the grave (if indeed even there).

Within the endless strife of living - strife over what is just as much as which material goods we can acquire - the scope of justice overlaps extensively with that of rationality and its practical weight is much the same as that of rationality, "a bond between persons, but not a very powerful bond". As for Plato, justice in the soul for Hampshire parallels justice in the city, though we learn what it is to be more coherent, both psychically and in our own actions, by attending to, and in some measure internalising, the more civilised and better considered procedures of adjudication and conflict mediation that prevail in the social settings we encounter.

At the core of these procedures, Hampshire sees the legal precept audi alteram partem - give the opposing case a proper hearing: a lesson he learnt from the late Herbert Hart, the only recent philosopher to whom he acknowledges a strictly personal debt in the course of the lectures themselves. Beyond this deceptively simple precept and the procedures that varyingly embody it, there is no universe of pre-given value, no ideal psychic equilibrium, nothing to stretch the imagination to reach or bend the will to obey. "The primary enemy from my standpoint is monotheism", with its God's-eye view of the way we and the world were meant to be, and the unitary theories of the good, or indeed the right, that that view encourages. Hampshire certainly rejects any form of moral universalism. But he also emphatically rejects nihilism (the presumption that human misery or hope do not intrinsically matter), seeing this less as a distinct metaphysical misconception than as a wanton and uninhibited hardening of the heart. In its place, defiantly, if perhaps a trifle cursorily, he reaffirms a form of democratic socialism that still hopes to extend the range of effective political agency to render human life together no longer brutally unequal and ravaged by misery. The main political virtue of socialism throughout its history he sees precisely as its recognition of the ineliminability of conflict from the organisation of work, production and exchange (a firmly selective reading from the full intellectual record), allied to its well-grounded and wholly honourable resistance to suffering and injustice.

The dawn of the third millennium is a time of very great political conservatism, of painfully chastened awareness of the difficulty of doing good, and the relative effortlessness of doing harm, by acting together.

Hampshire was pre-inured to the intellectual grounds for this shift of political sentiment, not least by his admiration for Hume and Burke. But he has conspicuously failed to trim his political tastes to its canons, and plainly still believes that you should think politics and economics not just by invoking highly abstract causal models of economic processes (as Rawls and Dworkin do), but also by trying to take in imaginatively the full human density, effort and pain that such models purport to transpose. It is not clear how far Hampshire's own tastes in political outcomes really differ from those of either Rawls or Dworkin. What is very clear by the end of his brief book is how deeply he disagrees with each, and with the great majority of contemporary political philosophers, over exactly how we must use our minds and imaginations to have any hope of comprehending what justice really is. I have no idea what Harvard made of its Tanner lectures on this occasion. But if I wanted to put into the hands of a clever adolescent one short book from the last half-century to show them why the nature of justice is as deep and treacherous a mystery as human life itself, I doubt if I could find one better than Justice is Conflict .

John Dunn is professor of political theory, University of Cambridge.