Tolstoy tells the story of an aristocratic woman at the theatre weeping at the imaginary tragedy enacted on the stage. At the same time, outside in the cold, a real tragedy is taking place: her old and faithful coachman, awaiting her in the bitter winter night, is freezing to death. The point of the story is obvious: art does not necessarily make people better behaved, or more considerate.

The dissociation between art and good behaviour angered Tolstoy and, in What is Art?, he savagely attacked what he perceived as the contemporary reduction of art to a mere amusement, recreation or opiate for the leisured classes. Against this, he asserted that 'art should be an organ co-equal with science for the life and progress of mankind'. And he defined art as an activity by which a man 'infected' his fellow men with feelings that he had himself experienced. The purpose of aesthetic form was simply to ensure that those feelings were transmitted effectively. Art should be judged not only according to how well the feelings were invoked but also according to the quality of the feelings themselves. Great art, which must be accessible to and significant to all men, to peasants as well as to the idle classes, transmits feelings that draw men together in brotherly union.

By these criteria, most of the art approved by his contemporaries could be dismissed: not only the works of Baudelaire, Wagner and Ibsen but much of Beethoven, Bach and Pushkin belonged to the category of bad art. And by the criterion of simplicity and accessibility, his own incomparable novels, whose greatness lay at least in part in their delineation of the complexity, ambiguity and vagaries of character, were worthless.

Tolstoy's late views - sharply at odds with earlier beliefs he had expressed with equal passion - are the more disturbing for emanating from the supreme practitioner of the art of fiction. In What Is Art? we recognise the ancestor of those doctrines that have fostered a thousand mediocre, state-sponsored novels in totalitarian regimes; the aesthetic that elevated 'tractor realism', in which cardboard cut-out revolutionary heroes struggle bravely and politically correctly against cardboard cut-out counter-revolutionary forces, above Pasternak and Mandelstam. Tolstoy's criterion of greatness in literature would certainly lead to some major re-evaluations: after all, Barbara Cartland's oeuvre is more accessible to the masses and contains more unequivocal examples of goodness and badness than, say, War and Peace.

Tolstoy's beliefs about the nature and purpose of art are too readily dismissed as part of the gathering madness of his old age, his descent from Tolstoy the artist of genius to Tolstoy the Tolstoyan. Even so, the belief that literature may be - indeed should be - a positive moral influence is tenacious. The opposite view - embodied in Wilde's assertion that 'there is no such thing as a moral or an immoral book. Books are well written or badly written. That is all' - can still shock even those who are not cultural commissars in totalitarian states.

Some critics claim, hope or imagine that literature may promote public morality; that the representations of the artist can deflect human society from a course dictated by greed, tyranny, cruelty, selfishness, vested interests, fear, servitude and the rest; that, by awakening the conscience of the oppressor and helping the oppressed to realise their power, art may hasten the reforms or the revolution that will bring oppression to an end. Others have emphasised the role of literature in promoting private morality, through refining our consciousness of others, our sensitivity to them, our ability to imagine into them.

It's not only critics but also artists themselves who believe in, or dream of, a morally useful art. For Keats true poets are 'those to whom the miseries of the world/ Are misery, and will not let them rest' - and this is asentiment shared by many can-temporary artists. Indeed, Martin Seymour-Smith has identified Künstlerschuld or artist-guilt as the occupational hazard of modern poets and writers who fear that 'literature fulfils no useful, only a selfish function'.

The claims made on behalf of politically engaged art are easily disposed of. History demonstrates that literature is as impotent as music in the face of tyranny and terror. Auden's assertion that 'poetry changes nothing' has been empirically proved again and again in the twentieth century. The eloquent outrage of great, humane writers has been and is unavailing - quite apart from the fact that a good many major artists have not been on the side of the angels anyway.

One should not be surprised at the political impotence of art Rigour, scrupulosity, precision, concern for the exact curve of the thing render the artist unfit for the kind of blunt, direct, usually one-sided, invariably simplifying and often dishonest communication that is most effective in political life. Great art does not simplify but makes more complex. The artist's deepest wish to see things whole undermines his polemic power: seeing all sides is the true glory of art and its utilitarian weakness. The sphere of public discourse is too shallow for the artist to swim in with his most powerful strokes. In the world of marches, public meetings and newpaper editorials, his is no longer a special, just another, voice. And a rather feeble one at that. You cannot chop down a tree with a scalpel. One editorial in the Sun newspaper has the opinion-forming clout of a thousand politically committed plays by, say, David Hare. Moreover, the artist has no particular authority or expertise outside of the aesthetic sphere - as is illustrated by the terrible misjudgements of passionately committed artists. Pound, Celine, Brecht, Gorky and others of equal stature lent their support, directly or indirectly, to The Great Terrors. Finally, works of art take time to create and to make their way in the public domain; so art is too late and too slow to intervene decisively in particular, evolving situations.

In short, good art - complex, ironic, self-questioning - is feeble propaganda, just as good propaganda, which tannoys the convenient wisdom, is bad art. Which is not to say that art should not have its political angers; they may flow from the generosity of its vision. But the angers, the generosity, while they add to the work's intrinsic merits, do not give it extrinsic force; they may be accounted part of its internal moral texture, not its external moral power. And the morality of art may lie as much in form as in content, in the distribution of light and shade as in what it shows forth in the light.

There may have been a time when art, and in particular literature, was less impotent: a period when mass literacy was novel, and relative political liberalism and the awakening of artists from the hierarchy in which they had occupied a subservient place, created a favourable context in which protest literature would not only be widely read but would also influence the thinking of those who could change things. If there was such a time - a golden age of Dickens and Uncle Tom's Cabin - it has now passed. This may be in part because the mass media have taken over much of the investigative and protest function of arts. The arts have lost those offices, just as they have shed responsibility for conveying practical information - the Georgics dimension. What poem could usefully add to our knowledge of, and our ability to alleviate the state of permanent atrocity that reigns in, Serbia, South Africa or Somalia?

Many of those who would concede, however regretfully, the impotence of art to influence the course of public events may still cling to the idea that it has a beneficent moral influence in the private sphere. Surely it will inspire better behaviour in ordinary individuals even if it is unable to reform power-mad tyrants, corrupt institutions and those whose vested interests lie in supporting them. The influence of art in heightening moral consciousness may be more subtle than that of the sermons, parables and plain tales Tolstoy saw as exemplars in What is Art? By showing us how people are destroyed by others, how they are corrupted, how they influence one another, do not, say, Henry James' novels increase our sensitivity to others' needs and vulnerabilities and, by enlarging our imaginative grasp of their lives - how they are made and unmade open us up to deeper, richer, more truly human relationships?

I am unaware of any empirical data to support this claim. The impact on individuals or populations of particular books, or of their cumulative reading experience, would be impossible to study and has not, so far as I know, been studied. All claims as to the morally beneficent effects of art must therefore be based on an a priori assumption and there are many reasons for regarding this assumption as intrinsically improbable.

The first, as is brilliantly illustrated by Tolstoy's story, is that the conditions under which one consumes art and the very business of being committed to art either as a consumer or a producer are more likely to subvert than to reinforce moral resolve. In order to pay art the attention it demands and perhaps deserves, we need to be insulated from the distractions of everyday life, including those that come from our suffering fellow humans - such as freezing coachmen. The consumer of art wants above all to be undisturbed and therefore creates the conditions, either explicitly or structurally (library, theatre, gallery, study), to ensure this.

Secondly, art fosters values that are orthogonal to those of everyday morality (and to describe those values as the basis of a 'deeper' morality is to beg the question); for example, aesthetic values relating to form, and values that transcend the 'merely' utilitarian - the 'merely', assumes that you're not hungry, oppressed or in pain - such as the preservation and celebration of past experience for its own sake. Art also generates secondary values of its own - those of the connoisseur, of the artsnob and of the scholar. The corruption implicit in such secondary values is illustrated by individuals whose reading prompts them to exhibit their erudition; for example, the writer who recalls Tolstoy's famous story of the freezing coachman not to learn from it but only in order to use it to support an argument about the relationship between art and morality.

Thirdly, the manner in which situations and dilemmas are packaged and presented in art is utterly different from the way in which they are presented in everyday life. Life recounted is inescapably different from life as it is lived. Even the soberest and least sentimental story has an operatic element and is a poor preparation for the plinthless actualities of ordinary life, for a world in which signals are inextricably caught up with noise (at least in part because twenty stories are going on at the same time). It is arguable that extensive reading of great. novels may corrupt one's judgement of, and response to, other people. After the brilliantly delineated characters on the page the companions of one's own life may seem drab, inferior and, above all, ill-defined. It is unlikely that the sentiments we feel, for literary characters whose lives we can see as a whole, and from within as well as from without, helpfully educate our emotions for, or train our responses to, real people. Anyway, as Whitehead pointed out, the emotions sought through art are largely 'cultivated for their own sake'. If the essence of sentimentality is expressed emotion separated from the commitment to action, imagined responses divorced from the most of the reality in which one would have to act, are, the 'contemplation of the object independently of the will to act upon it', must be quintessentially sentimental. The truth is that art is primarily a spectacle or a reduction of the world to a spectacle. Certainly, representations on the scale and ambition and complexity of novels must develop the detached, speciatorial element in us. Even those novels that are not intended as jewels to be contemplated in abstraction from the world, but lenses through which we see the world more clearly and brightly, are weak moral motors. Tolstoy's expectation that 'the feelings awoken by art would lay in the souls of men the rails along which our actions will naturally pass' seems a pious hope - however great, sincere moral or earnest the art.

I have so far assumed that the emotions stimulated by literature would be intrinsically good. This may not always be the case. Even identification with characters who have endured injustice or undergone some ordeal may be in some degree masochistic. Fantasies of being subjected to injustice and subsequent vindication (the latter with a completeness possible only in represented worlds) are all-pervasive in literature - in The Winter's Tale as much as in rescue operas or Westerns. Such emotions are infantile and corrupting, firing dreams of satisfaction and moral revenge. And there are, of course other, darker emotional pleasures to be derived from literature.

It may be that the moral influence of good art is more indirect than has been considered here. In reply to an interviewer's assertion that 'Art can be considered good only as it prompts to action', Robert Frost famously said 'How soon?' However, the assumption that art may not have an immediate beneficial effect but may result indirectly in such effects ('the unacknowledged legislators of the world' fantasy) must be at best speculative. For once we start thinking about indirect and remote effects, we are into the realm of total uncertainty. Chaos theory has taught us that causation in complex dynamical systems - and what system could be more complex than the interaction between a book, a reader and the world? - is unpredictable and untraceable once one goes beyond a couple of steps in the chain.

The claim for the power of art as a moral influence - to improve public or private, individual or collective behaviour - seems baseless. Is art therefore without value? Should the government cease to sponsor art since it will not make the people better citizens? Should parents discourage their children from reading great literature, since it will not make them kinder in their private lives? Of course not. While art may not make individuals morally better, it will introduce them to a greater selection of the meanings that the world may have and so widen and deepen their experience of life. Though art is impotent to change the course of history for the better its image of the terrible and wonderful things that happen in history may in some small sense redeem them, if only for a privileged few: helpless to intervene, it will bear witness, and be true to, the world. Indeed, without taking account of the terrible, art will be empty, trivial; and there may be an element of ordeal in the experience of a great work of art. A masterpiece is a place where many disparate, partial meanings meet and are synthesised into a whole; a utopia of consciousness where much that is scattered or fragmented in life is drawn together.

When he said that a pair of old boots was of more use than the entire works of Shakespeare, Nekrasov - who was the first to discover and promote Tolstoy's genius - was not condemning art, but clarifying its function. Art is only weakly effective in the utilitarian world of practical need and practical morality. Its true sphere is the kingdom of ends: it addresses the final purposes of life rather than the means by which life (and comfort and safety and freedom from want or terror) may be secured. And although it has only a slight external moral force, it does have an intrinsic morality. This is evident in Tolstoy's own incomparable novels. They illuminate the world with an even and just light, and reach with a generosity of imagination into all sorts and conditions of humanity, linking the great facts that enclose us - that we are unoccasioned, that we are transient, that we nonetheless make the world our own thing - with the small facts that detain us. The temptation to believe that this will translate into an influence on practical morality - on behaviour in the public or the private sphere so that with a finer awareness will come a richer, deeper sense of practical responsibility, may be overcome by remembering the weeping princess in the theatre and the coachman freezing to death outside.

This piece first appeared as a talk on Radio 3 in 1993.