The British Museum is undergoing a major overhaul. As part of this revamp, it has just opened a set of three new galleries devoted to late Bronze Age Europe, Celtic Europe and Roman Britain, a period from roughly 2,500 BC to the fifth century AD.

The new galleries are a permanent exhibition intended to give an authoritative interpretation of three millennia of history that will stand for a generation. But one of them has already proved to be surprisingly controversial. Simon James, a curator of the Museum and fellow of Durham University, has challenged the validity of the title Celtic Europe. He writes, 'Everyone has heard of the Celts. Yet more and more archaeologists are concluding that the Ancient Celts, as usually conceived, never really existed.' As a result, he says, he has received e-mails accusing him of 'ethnic cleansing' and 'genocide'.

According to James, 'the 'Ancient Celts' were not so much discovered, as gradually invented by generations of scholars.' On the other side there are academics who argue that the Celts are the ancestors of the modern Irish, Scots, Welsh and Bretons, and that attempts to deny this are racist. The dispute has become so bitter and personal that academics writing in learned journals have even felt called upon to explain the ethnic origins of their grandmothers. When all this invective is put on one side, what appears at first sight to be a fairly straightforward two-sided contest becomes more complex.

Few archaeologists deny the existence of the Celts in the European Iron Age, the period from roughly the mid-eighth century BC to the Roman conquest. As late as 1993, James himself wrote a book entitled, Exploring the World of the Celts. Taken as a whole, the evidence of their existence is remarkably good for such an early historical period. Greek and Roman authors recognised a people whom they called variously the Keltoi, Galli or Galatians. In the fourth century BC they tell us that the Celts sacked Rome and sent ambassadors to the court of Alexander the Great in Babylon. In the third century BC a party of Celtic warriors sacked Delphi in Greece while three tribes settled in what is now Turkey. Their descendants were still called Galatians when St. Paul wrote to them in the first century AD. The Romans fought the Celts in Northern Italy, Spain and France for over 300 years. When they were not fighting, the archaeological record shows that they were trading with one another.

As their territories were conquered Celts were absorbed into Roman society while remaining conscious of their distinct identity. The Roman poet Martial was proud of his Celtic ancestry. Julius Caesar, who defeated Celtic tribes in what is now France, left a comparatively detailed account of their social and political organisation. He indicates that there were close cultural links between Britain and continental Europe. A growing body of evidence from inscriptions found on the continent confirms this view. They show that in Spain and Northern Italy languages were spoken that are related to modern Welsh, Gaelic and Breton. What is more, some of the gods and religious festivals of pagan Ireland share the same names as those recorded among Celts on the continent.

Certainly, there are problems in relating the linguistic, archaeological and written evidence to one another. As one would expect at such an early period of European history, large gaps remain in our knowledge and some questions can never be answered with any certainty. But to argue about the existence or non-existence of the Celts is not a genuine historical controversy. For it to raise such passion suggests that an unstated issue of considerably more substance lies behind the public dispute.

The argument is not really about whether the Celts existed or not, but about what history is and the nature of historical facts. It is about whether history should be scientific or mystical. The archaeologist Vere Gordon Childe dealt with this question in the opening chapter of his book Man Makes Himself in 1936.

Writing in the aftermath of World War I and the Great Depression and with another war looming, Childe recognised that the optimistic belief in progress so prevalent in the nineteenth century had faded. A new spirit of mysticism and obscurantism was influencing society at large and the study of history. He set out to demonstrate human progress through the prehistoric period, as an antidote to the fascist ideology which had set archaeologists searching for the origins of the Nazi super-race and to the sentimental nostalgia for the pre-industrial past that suffused much liberal and left-wing thought of the period.

While in his lifetime Childe was attacked by other archaeologist for his adherence to Marxism, after his death in 1957 he came under attack from left-wing radicals influenced by structuralism and the Frankfurt school who, responding to the crimes of fascism and especially Stalinism, rejected the conception of historical progress. His attempt to apply the Marxist theory of social evolution to archaeology was condemned by a united chorus of left and right, but his contribution to the discipline was too great to be ignored. His conception of archaeology as an objective, scientific approach to culture history, essentially economic and social history, focusing on the study of how people made a living, their technology and their social organisation, became the accepted form of archaeology.

What is remarkable about the British Museum exhibition, although in all the controversy over the Celts it has gone unremarked, is the extent to which it has moved away from this approach and returned to an antiquarian, collector's style which pre-dates Childe. The cases are refulgent with precious metal. It is an exhibition that dazzles the eye, but leaves the intellect unsatisfied. By what process all this wealth was acquired and what social relations allowed some people to accumulate it, the visitor is not informed.

The interpretation of Iron Age Europe that the British Museum is offering is a step away from science. Central to this non-scientific approach is a concentration on ethnicity. The problem with the exhibition is not just that it elevates the Celts at the expense of the Tartessians, the Ligurians, the Iberians and all the people of Iron Age Europe that we cannot name, but that it presents ethnicity as the most appropriate conceptual basis for the study of history. Ethnicity is not an appropriate category for historical analysis because it tells us nothing about the people concerned. It does not tell us what kind of agriculture, if any, they practised. It does not tell us what tools and equipment were at their disposal. It does not tell us how their society was organised. It does not even tell us what their relations were with other ethnic groups.

Above all, it does not tell us how the ethnic group changed through time, but instead imposes a timeless quality on the past that is ahistorical. For example, the Celts of Lugdunensis, modern Lyon in southern France, worshipped the god Lugh whose festival, Lugnasad, was on 1 August. The same god was venerated and the same festival observed in Ireland until the coming of Christianity in the fifth century AD. But we cannot assume that the god or the festival held the same significance for the relatively sophisticated and, even before the Romans came, increasingly urbanised population of southern France and the inhabitants of economically backward Ireland where no towns developed until the early medieval period. Celts they may both have been, but their worlds were very different.

Compared to some archaeologists the British Museum is only dipping its toes in the water of ethnic history. Its most vigorous champions are Vincent and Ruth Megaw from Flinders University in Australia, who specialise in the study of Celtic art. Appropriately enough they defended their ethnic approach to history at an archaeological conference in Slovenia, part of the former Yugoslavia. There they put forward an arbitrary and subjective definition of ethnicity, which was internally contradictory and scientifically invalid.

They argued that ethnicity cannot be defined in genetic terms, nor on the basis of language or culture, but is part of a 'landscape of the mind'. They gave the example of an Australian Aboriginal artist friend of mixed Aboriginal, Irish and German descent, who sometimes identifies herself by the local Aboriginal group from which her father came, sometimes by the wider group of South East Australian Aboriginals, in yet in other contexts simply as an Australian Aboriginal. Ethnicity, the Megaws claim, is a subjective category in which the past is remembered selectively and in which symbols--often of a religious character, as in Bosnia and Northern Ireland--are used to define identity. To deny someone's belief in their ethnic identity is inherently racist according to the Megaws.

True to their ethnic approach, the Megaws identify their opponents as certain English archaeologists who wish to deny the existence of the Celts because of the 'ethnography of the archaeology profession' in England. This is where grandmothers come into the argument. Englishmen, in the Megaws' view, cannot write history if it involves Celts.

English archaeologists, they explain, are gripped by an ideological crisis that is bound up with a redefinition of English identity following the end of the British Empire. Britain has become a multicultural society and concerns about the effects of this transformation, which cannot be expressed legally, emerge in a distorted form in the academic world. At the same time British sovereignty is under threat internally from devolution and externally from the European union. For the 'English mind' the Celts have become a symbol of both the threat of internal disintegration and external control. In this way the Megaws construct a stereotype of English archaeologists as far right Tory Europhobes, wrapping themselves in the Union Jack, barely concealing their hatred of Asians and West Indians behind their denial of the Celts' existence.

An article based on their Ljubljana paper was published in Antiquity, one of the leading British archaeological journals. It succeeded in raising the temperature of the debate and putting every archaeologist writing about the Celts on the defensive. Archaeologists now preface their comments with an account of their own ethnic origins, and assure the reader that they are sympathetic to progressive causes.

This is a dangerous turn of events. To imply that only those who are from an ethnic group can write about it is to undermine the study of history. To imply that only those with a certain political outlook can write good history is just as damaging. While interpretations may vary widely, historical facts have a certain objective validity that can be discerned by anyone who approaches the subject with honesty and a critical frame of mind. The Megaws have attacked the principle that history is an objective study of the past. In this respect many archaeologists and historians today would agree with them.

Simon James's extraordinary denial of the existence of the Celts seems to be partially motivated by a desire to oppose this ethnic approach to history. Yet at the same time he agrees with the Megaws that history is entirely subjective. He claims that the Celts are merely a subjective construct created by previous generations of historians for their own ideological reasons and are therefore no more real than the mythical tribes of Centaurs and Amazons that the Greeks believed lived beyond the Black Sea.

This is a superficial argument that is only given credence because of a general decline in the quality of intellectual life. The Hellenistic imagination was indeed fertile. It populated little known regions with fantastic tribes. The Celts, however, are not among them. St. Paul never had occasion to write a pastoral letter to the Amazons or the Centaurs. The Celts are an historical fact. The idea that because different historians have different interpretations of history there is no such thing as an historical fact is a characteristic feature of postmodernism. It reduces historical study to an exercise in futility that has nothing of any value to say about human society.

Announcing their new galleries, the British Museum make a point of the care they had taken to avoid any hint that in prehistory it was possible to discern a process of human progress through social evolution. More than anyone it was Childe who attempted to apply a theory of social evolution to archaeology. By rejecting this, archaeologists are denying themselves a scientific basis for their discipline and laying themselves open to attacks like that of the Megaws.

The vestiges of Childe's approach that survive in the form of an archaeology based on culture history dealing with questions of social and economic organisation still produces some of the best studies. Into this category falls Barry Cunliffe's recent book The Ancient Celts. While no evolutionist, and no Marxist, Cunliffe offers a serious study of Celtic society. A reader may accept or reject aspects of his analysis, but it is always well founded on fact. The British Museum hope that their interpretation of prehistoric Europe will establish the orthodoxy for the next generation, but faced with the bleak and baffling perplexities of postmodernism many students will be repelled from the subject of history in disgust. Those who persist and want to make some sense of the prehistoric past would do well to re-examine Childe.