How does personality affect politics? Huw Richards considers the academic perspectives.

To what extent can an individual affect history? Are individuals wholly independent actors or entirely the prisoners of the context provided by broad, long-term historical forces? Pitting historical determinism against "one damn thing after another" and theory against narrative, such questions are history's version of one of the most elemental of human debates - do humans have free will?

Personality and politics interact at many levels and could embrace individuals' ability to alter the great sweep of history or merely the fortunes of a single state. The "personality" question may imply individual character quirks and idiosyncrasies. Or it might invoke one of the most basic of political science issues: how far an individual candidate or leader can affect the fortunes of a party at local or national level. It raises issues that all historians must address.

E. H. Carr's What Is History? (1961) may have cast him as a spokesman for determinism, but in planning for the book's second edition 20 years later, he was prepared to accept that Lenin's premature death and Stalin's succession had, in the short term at least, a significant impact on life in Russia and that "even if you maintain that in the long run everything would have turned out much the same, there is a short run which is very important and makes a great deal of difference to a great many people".

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Similarly A. J. P. Taylor may famously have written (1950) that "The history of modern Europe can be written in terms of three Titans: Napoleon, Bismarck and Lenin", but he also quoted approvingly Bismarck's dictum: "Man cannot create the current of events. He can only float with it and steer."

Historians also reflect their times. Pieter Geyl in Napoleon For and Against (1949) and Georges Rude in Robespierre (1975) noted the tendency of successive generations of historians to reinterpret individuals and events in the light of their own age. Rude pointed out that the liberal, anti-clerical historians of the early Third Republic (1870 on) tended to admire Robespierre's great rival, Danton, but that growing Marxist influence, the first world war and Russian revolution in the first two decades of the 20th century produced a swing towards Robespierre.

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Another factor is perspective. As Eric Hobsbawm said of the shift by Emanuel Le Roy Ladurie from the large-scale statistical analysis of Les Paysans du Languedoc (1966) to the intensive examination of a single small community in Montaillou (1976), it is as legitimate to study history through a microscope as through a telescope. And to write biography is by definition to regard the individual as significant.

Early written history was predominantly biographical - the lives of saints and kings. The individual forms the whole of the picture. This exclusive emphasis changes once historians start looking to documentary sources to reconstruct the past - a process that in Britain has been dated to Gilbert Burnet's History of the Reformation in England (1679). It was systematised by the German Leopold von Ranke (1795-1886), founding father of history as a profession. Ranke's exhaustive studies examining history over long periods told him that "every life of historical significance has a determined content", but even his was still history from above, focusing on rulers and their policies.

Britain has a long biographical tradition centred on the individual political actor. This reached an early apotheosis with Thomas Carlyle, whose books included a life of Cromwell and Heroes and Hero-Worship (1841).

Victorian politics spawned vast multi-volume biographies of major figures such as John Morley's Life of Gladstone (1903), minutely detailing their public lives.

Disraeli summed up part of biography's appeal as: "History with the theory left out." Emphasis on the individual actor comes naturally to those who see history as closer to literature than to social science and are wary of broad theoretical frameworks derived from other disciplines. It was no surprise that Sir Geoffrey Elton should emphasise the personal role of Thomas Cromwell in the Tudor Revolution in Government (1953) and be one of E. H. Carr's most trenchant critics with The Practice of History (1967).

Yet even Carlyle saw political causation beyond the great man - citing "Hunger and Nakedness and righteous oppression lying heavy on 25 million hearts" as the prime cause of the French revolution. That history might be impelled from below as well as from above, by masses as well as individuals, was the contention of Jules Michelet, whose history of the revolution (1847) stated " l'acteur principal est le peuple ". Notable followers of this approach have included George Lefebvre ( La Grande Peur de 1789, 1932 ) and E. P. Thompson ( The Making of the English Working Class (1965).

Approaches treating the individual as prisoner or, at best, agent of broader forces are most strongly associated with Karl Marx. But his influence is felt well beyond those who would call themselves, or be called, Marxists. It was Arthur Schlesinger Sr who declared that the "Great Man" is "merely the mechanism through which the Great Many have spoken".

Since the 1920s, the French annaliste school has stressed geography and the long term. Its key work, Fernand Braudel's The Mediterranean and the Mediterranean World in the Age of Phillip II (1949), has been described as "concerned to place individuals and events in a wider context, to make them more intelligible at the price of revealing their fundamental lack of importance".

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In the 1950s and 1960s, impetus did seem to be with those who stressed the social science approach. S. T. Bindoff, contributing to a 1962 symposium on approaches to history, noted a tendency to play down the individual. This was particularly strong in countries such as West Germany, where, Richard Evans has noted, historians reacting against the cult of personality under Hitler "avoided biography and concentrated on writing the history of people in the past mainly as a history of averages, groups and global trends".

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But the traffic was not all one way. Isaiah Berlin responded to E. H. Carr's assault on "the assumption that the important explanations in history are to be found in the conscious purposes of the dramatis personae " with his Historical Inevitability (1954), arguing that man's unique quality was a capacity for choice. External forces did limit individuals, but it was the historian's job to identify how much room they had to manoeuvre and what possible courses of action were available - and to judge them accordingly.

In 1979, Lawrence Stone identified a "revival of narrative", arguing that the social sciences had done a great deal for history but had not delivered the overarching syntheses they had promised. Certainly, biography has enjoyed a comeback since the 1950s.

Over the past century, psychology has been persistently significant.

Havelock Ellis complained in the 1890s that biographers did not tell him "a fair proportion of what I wish to know". This changed in many biographies after Freud, whose proponents included Sir Lewis Namier. He argued in 1955 that: "History is primarily, and to a growing extent, made by man's mind and nature; but his mind does not work with the rationality that was once deemed its noblest attribute."

In British political science, David Butler found that individual candidates might change a few hundred votes at the most per constituency. And Dennis Kavanagh, writing at the end of Margaret Thatcher's highly personalised premiership, noted that - with the exception of Churchill in wartime - leaders' approval ratings generally parallel those of their party or government within a few points. This might seem to diminish the impact of personality, but Butler noted that most elections are decided at the margins.

While "high politics", emphasising the actions of individual politicians rather than wider social forces, has often been identified with the political right, it could be argued that the historiography of the left has benefited more from the greater emphasis on biography through major works such as David Marquand's Ramsay McDonald (1978), Philip Williams' Hugh Gaitskell (1979), Ben Pimlott's Hugh Dalton (1985) and Harold Wilson (1992) and Peter Clarke's The Cripps Version (2002). One element in this may be that more of the left's major figures - Dalton, Gaitskell, Richard Crossman and Tony Benn among them - were diarists, while the right's diarists such as "Chips" Channon and Alan Clark tended to be better writers than politicians. Diaries were increasingly identified as a vital source by historians such as Pimlott, who argued that biography could and should benefit from the techniques of literature and of social science.

Others were unconvinced. Williams' Gaitskell, regarded as a magnificent political biography, avoided some aspects of his subject's private life.

Ellis would have been happier with Brian Brivati's Hugh Gaitskell (1996), which devoted several pages to Gaitskell's affair with Tory hostess Ann Fleming.

Abroad, the reaction to personality cults has led to British rather than native writers producing what are widely recognised as the standard works on the major figures of Spanish and German 20th-century history - Paul Preston's Franco (1993) and Ian Kershaw's two-volume Hitler (1998, 2000).

But "the biographical turn" is evidently in force generally, with German historians in particular turning to biography - illustrating unexplored aspects of Nazism through the lives of those who epitomise them.

Such trends are accentuated by the influence of postmodernism, with its distrust of anything that looks like grand theory. Opinion varies sharply on the value of counterfactual volumes in the "What if...?" vein. Critics argue that they are in essence entertainments of little more intrinsic historical value than the humorous classic of the genre, James Thurber's What if Grant Had Been Drunk at Appomattox? . But in their emphasis on the significance of single actions they, as much as more conventional biography, demonstrate a modern appetite for history centred on the individual.

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