and then bringing them to naught. Very similar is the rôle in history assigned by von Hartmann to his ‘Unconscious.’ “It carries away the peoples that it dominates,” says von Hartmann, “with a demoniac power towards unknown ends; it teaches them the way that they must take; though they often believe themselves to be marching towards a goal very different from that to which they are being conducted.” Others maintain that the great men of a nation, who are the principal agents in moulding its destiny, are in some mystical sense the products and expressions of the ‘unconscious soul’ of the people, that they are the means by which its ideas are realised, through which they become effective; and they usually make the assertion, altogether unwarranted by history, that the moment of great need in the life of a people always produces a great man or hero to lead the people through the crisis. That is, or may appear to be, true of those peoples that have survived to pass into history. But what of those peoples that have gone down, leaving no trace of all their strivings, beyond some mounds of rubble, some few material monuments, or some strange marks on brick or stone or rock? All such assumptions are the very negation of science. We have no right to appeal to such obscure and mystical powers, until by prolonged effort we shall have exhausted the possibilities of understanding and explanation in terms of known forces and conditions[47]. On the other hand, a number of writers have sought to interpret the course of history and the rise and fall of nations in a more scientific manner; but most of these have studied some one aspect of national life, and have professed to find in that one aspect the key which shall unlock all doors and solve all problems. Thus some, adopting the notion of a variety of human races, each endowed with a certain peculiar and unalterable combination of qualities, seek to explain all history by the aid of biological laws, especially the Darwinian principles, as a struggle for survival between individuals and between races. Others, like Karl Marx and Guizot, see in economic conditions and the struggles between the social classes within each nation, the all important factors. Others again, like Montesquieu and to some extent Buckle and more recently Matteuzzi, have seen in the influences of physical environment the key to the understanding of differences of national character and history; while others profess to have found it in differences of religious system, or of the forms of government and systems of laws. Others again, like le Bon[48], in a few dominant ideas which, they say, being possessed by any nation (or possessing a nation) determine its character and civilisation. All these are exaggerations of partial truths; and in opposition to all of them it must be laid down that the understanding of the _mind_ of a nation is an indispensable foundation for the interpretation of its history.