It is an error to regard the imagination as a mainly revolutionary force - if it destroys and alters, it also fuses hitherto isolated beliefs, insights, mental habits, into strongly unified systems. These, if they are filled with sufficient energy and force of will - and, it may be added, fantasy, which is less frightened by the facts and creates ideal models in terms of which the facts are ordered in the mind - sometimes transform the outlook of an entire people and generation.

     The British statesman most richly endowed with these gifts was Disraeli, who in effect conceived that imperialist mystique, that splendid but most un-English vision which, romantic to the point of exoticism, full of metaphysical emotion, to all appearances utterly opposed to everything most soberly empirical, utilitarian, anti-systematic in the British tradition, bound its spell on the mind of England for two generations.

     Churchill's political imagination has something of the same magical power to transform. it is a magic which belongs equally to demagogues and great democratic leaders: Franklin Roosevelt, who as much as any man altered his country's inner image of itself and of its character and its history, possessed it in a high degree. But the differences between him and the Prime Minister of Britain are greater than the similarities, and to some degree epitomize the differences of continents and civilisations. The contrast is brought out vividly by the respective parts which they played in the war which drew them so closely together.

     The Second World War in some ways gave birth to less novelty and genius than the First. It was, of course, a greater cataclysm, fought over a wider area, and altered the social and political contours of the world at least as radically as its predecessor, perhaps more so. But the break in continuity in 1914 was far more violent. The years before 1914 look to us now, and looked even in the 1920s, as the end of a long period of largely peaceful development, broken suddenly and catastrophically. In Europe, at least, the years before 1914 were viewed with understandable nostalgia by those who after them know no real peace.

     The period between the wars marks a decline in the development of human culture if it is compared with that sustained and fruitful period which makes the nineteenth century seem a unique human achievement, so powerful that it persisted, even during the war which broke it, to a degree which seems astonishing to us now. The quality of literature, for example, which is surely one of the most reliable criteria of intellectual and moral vitality, was incomparably higher during the war of 1914-18 than it has been after 1939. In western Europe alone these four years of slaughter and destruction were also years in which works of genius and talent continued to be produced by such established writers as Shaw and Wells and Kipling, Hauptmann and Gide, Chesterson and Arnold Bennett, Beerbohm and Yeats, as well as such younger writers as Proust and Joyce, Virginia Woolf and E.M. Forster, T.S. Eliot and Alexander Blok, Rilke, Stefan George and Valéry. Nor did natural science, philosophy and history cease to develop fruitfully. What has the recent war to offer by comparison?

     Yet perhaps there is one respect in which the Second World War did outshine its predecessor: the leaders of the nations involved in it were, with the significant exception of France, men of greater stature, psychologically more interesting, than their prototypes. It would hardly be disputed that Stalin is a more interesting figure than the Tsar Nicholas II; Hitler more arresting than the Kaiser; Mussolini than Victor Emmanuel; and, memorable as they were, President Wilson and Lloyd George yield in the attribute of sheer historical magnitude to Franklin Roosevelt and Winston Churchill.

     'History,' we are told by Aristotle, 'is what Alcibiades did and suffered.' This notion, despite all the efforts of the social sciences to overthrow it, remain a good deal more valid than rival hypotheses, provided that history is defined as that which historians do. At any rate Churchill accepts it wholeheartedly, and takes full advantage of his opportunities. And because his narrative deals largely in personalities and gives individual genius its full and sometimes more than full due, the appearance of the great wartime protagonists in his pages gives his narrative some of the quality of an epic, whose heroes and villains acquire their statue not merely - or indeed at all - from the importance of the events in which they are involved, but from their own intrinsic human size upon the stage human history; their characteristics, involved as they are in perpetual juxtaposition with one another, set each other off in vast relief.

     Comparisons and contrasts are bound to rise in the mind of the reader which sometimes take him beyond Churchill's pages. Thus Roosevelt stands out principally by his astonishing appetite for life and by his apparently complete freedom from fear of the future; as a man who welcomed the future eagerly as such, and conveyed the feeling that whatever the times might bring, all would be grist to his mill, nothing would be too formidable or crushing to be subdued and used and moulded into the pattern of the new and unpredictable form of life, into the building of which he, Roosevelt, and his allies and devoted subordinates would throw themselves with unheard energy and gusto. This avid anticipation of the future, the lack of nervous fear that the wave might prove too big or violent to navigate, contrasts most sharply with the uneasy longing to insulate themselves so clear in Stalin or Chamberlain. Hitler, too, in a sense, showed no fear, but his assurance sprang from a lunatic's violent and cunning vision, which distorted the facts too easily in his favour.

     So passionate a faith in the future, so untroubled a confidence in one's power to mould it, when it is allied to a capacity for realistic appraisal of its true contours, implies an exceptionally sensitive awareness, conscious or half-conscious, of the tendencies of one's milieu, of the desires, hopes, fears, loves, hatreds, of the human beings who compose it, of what are impersonally described as social and individual 'trends.' Roosevelt had this sensibility developed to the point of genius. He acquired the symbolic significance which he retained throughout his presidency, largely because he sensed the tendencies of his time and their projections into the future to a most uncommon degree. His sense, not only of the movement of American public opinion but of the general direction in which the larger human society of his time was moving, was what is called uncanny. The inner current, the tremors and complicated convolutions of this movement, seemed to register themselves within his nervous system with a kind of seismographical accuracy. The majority of his fellow-citizens recongised this - some with enthusiasm, others with gloom or bitter indignation. Peoples far beyond the frontiers of the United States rightly looked to him as the most genuine and unswerving spokesman of democracy of his time, the most contemporary, the most outward-looking, free from the obsessions of the inner life, with an unparalleled capacity for creating confidence in the power of his insight, his foresight, and his capacity genuinely to identify with the ideals of humble people.

     The feeling of being at home not merely in the present but in the future, of knowing where he was going and by what means and why, made him, until his health was finally undermined, buoyant and gay: made him delight in the company varied and opposed individuals, provided that they embodied some specific aspect of the turbulent stream of life, stood actively for the forward movement in their particular world, whatever it might be. And this inner élan made up, and more than made up, for faults of intellect or character which his enemies - and his victims - never ceased to point out. He seemed genuinely unaffected by their taunts: what he could not abide was, before all, passivity, stillness, melancholy, fear of life or preoccupation with eternity or death, however great the insight or delicate the sensibility by which they were accompanied.

     Churchill stands at almost the opposite pole. He too does not fear the future, and no man has ever loved life more vehemently and infused so much of it into everyone and everything that he has touched. But whereas Roosevelt, like all great innovators, had a half-conscious premonitory awareness of the coming shape of a society, not wholly unlike that of an artist, Churchill, for all his extrovert air, looks within, and his strongest sense is the sense of the past.

     The clear, brightly coloured vision of history, in terms which he conceived both the present and the future, is the inexhaustible source from which he draws the primary stuff out of which his universe is so solidly built, so richly and elaborately ornamented. So firm and so embracing an edifice could not be constructed by anyone liable to react and respond like a sensitive instrument to the perpetually changing moods and directions of other persons or institutions or peoples. And, indeed, Churchill's strength (and what is most frightening in him) lies precisely in this: that, unlike Roosevelt, he is not equipped with numberless sensitive antennae which communicate with the smallest oscillations of the other worlds in all its unstable variety. Unlike Roosevelt (and unlike Gladstone and Lloyd George for that matter) he does not reflect a contemporary social or moral world in an intense and concentrated fashion; rather he creates one of such power and coherence that it becomes reality and alters the external world by being imposed on it with irresistible force. As his history of the war shows, he has an immense capacity for absorbing facts, but they emerge transformed by the categories which he powerfully imposes on the raw material into something which he can use to build his own massive, simply, impregnably fortified inner world.

     Roosevelt, as a public personality, was a spontaneous, optimistic, pleasure-loving ruler who dismayed his assistants by the gay and apparently heedless abandon with which he seemed to delight in pursuing two or more totally incompatible policies, and astonished them even more by the swiftness and ease with which he managed to throw off the cares of office during the darkest and most dangerous moments. Churchill too loves pleasure, and he too lacks neither gaiety nor a capacity for exuberant self-expression, together with the habit of blithely cutting Gordian knots in a manner which often upset his experts; but he is not a frivolous man. His nature possesses a dimension of depth - and a corresponding sense of tragic possibilities - which Roosevelt's light-hearted genius instinctively passed by.

     Roosevelt played the game of politics with virtuosity, and both his successes and his failures were carried off in splendid style; his performance seemed to flow with effortless skill. Churchill is acquainted with darkness as well as light. Like all inhabitants and even transient visitors of inner worlds, he gives evidence of seasons of agonised brooding and slow recovery. Roosevelt might have spoken of sweat and blood, but when Churchill offered his people tears, he spoke a word which might have been uttered by Lincoln or Mazzini or Cromwell, but not by Roosevelt, great-hearted, generous and perceptive as he was.