the belief that history provides examples and warnings to statesmen is as ancient, at least, as Thucydides, and the passage quoted above from Lord Acton's inaugural lecture may well have been intended and taken as little more than a reassuring and timeless platitude. Nevertheless, the thought of the nineteenth century had been, as Acton went on to say, imbued to an extraordinary extent with a sense of the importance of the historical perspective. It was an influence which left its stamp on attempts to confront the requirements of a science of politics in various ways, some of which we have already seen in considering Macaulay, J. S. Mill and Bagehot.