This treatise of historical methodology, originally published in 1950 is based upon a liberal conception of history which excludes no narrator of past events from the ranks of historians. It defines history as the accurae story which preserves the memory of the past experiences of human societies. The functionof history determines its method and provides the answer to the question: how secure is our knowledge of the past? In the author's view, history is empirical and its results are for ever provisional. The relative merits of dogmatism and scepticism are examined and several interpretations among English historians are scrutinized.