Above all, history – social and economic structure – and politics divided the revolutionary zone into two parts, whose extremes appeared to have litt… - Eric Hobsbawm

History, whose subject is the past, is not in a position to be an applied discipline in this sense, if only because no way has yet been discovered to change what has already happened. At most we can make counterfactual speculations about hypothetical alternatives. Of course past, present and future are part of one continuum, and what historians have to say could therefore permit both forecasts and recommendations for the future.

Where historians try to come to grips with a period which has left surviving eyewitnesses, two quite different concepts of history clash, or, in the best of cases, supplement each other: the scholarly and the existential, archive and personal memory. For everyone is a historian of his or her own consciously lived lifetime inasmuch as he or she comes to terms with it in the mind – an unreliable historian from most points of view, as anyone knows who has ventured into ‘oral history’, but one whose contribution is essential. Scholars who interview old soldiers or politicians will have already acquired more, and more reliable, information about what happened from print and paper, than their source has in his or her memory, but may nevertheless misunderstand it. And, unlike, say, the historian of the crusades, the historian of the Second World War can be corrected by those who, remembering, shake their head and tell him or her: ‘But it was not like that at all.’ Nevertheless, both the versions of history which thus confront one another are, in different senses, coherent constructions of the past, consciously held as such and at least potentially capable of definition.

Most observers in the 1870s would have been far more impressed by its linearity. In material terms, in terms of knowledge and the capacity to transform nature it seemed so patent that change meant advance that history – at all events modern history – seemed to equal progress. Progress was measured by the ever rising curve of whatever could be measured, or what men chose to measure. Continuous improvement, even of those things which clearly still required it, was guaranteed by historical experience. It seemed hardly credible that little more than three centuries ago intelligent Europeans had regarded the agriculture, military techniques and even the medicine of the ancient Romans as the model for their own, that a bare two centuries ago there could be a serious debate about whether the moderns could ever surpass the achievement of the ancients, and that at the end of the eighteenth century experts could have doubted whether the population of Britain was increasing.