The title and much of the substance of the present volume might lead a hasty reader to suppose that I am influenced by, or even in sympathy with, the political philosophy associated with German ‘idealism.’ I would, therefore, take this opportunity both to prevent any such erroneous inference and to indicate my attitude towards that system of thought in plainer language than it seemed possible to use before the war. I have argued that we may properly speak of a group mind, and that each of the most developed nations of the present time may be regarded as in process of developing a group mind. This must lay me open to the suspicion of favouring the political philosophy which makes of the state a super-individual and semi-divine person before whom all men must bow down, renouncing their claims to freedom of judgment and action; the political philosophy in short of German ‘idealism,’ which derives in the main from Hegel, which has been so ably represented in this country by Dr Bosanquet, which has exerted so great an influence at Oxford, and which in my opinion is as detrimental to honest and clear thinking as it has proved to be destructive of political morality in its native country. I am relieved of the necessity of attempting to justify these severe strictures by the recent publication of _The Metaphysical Theory of the State_ by Prof. L. T. Hobhouse. In that volume Prof. Hobhouse has subjected the political philosophy of German ‘idealism,’ and especially Dr Bosanquet’s presentation of it, to a criticism which, as it seems to me, should suffice to expose the hollowness of its claims to all men for all time; and I cannot better define my own attitude towards it than by expressing the completeness of my sympathy with the searching criticism of Mr Hobhouse’s essay. In my youth I was misled into supposing that the Germans were the possessors of a peculiar wisdom; and I have spent a large part of my life in discovering, in one field of science after another, that I was mistaken. I can always read the works of some German philosophers, especially those of Hermann Lotze, with admiration and profit; but I have no longer any desire to contend with the great systems of ‘idealism,’ and I think it a cruel waste that the best years of the lives of many young men should be spent struggling with the obscure phrases in which Kant sought to express his profound and subtle thought. My first scientific effort was to find evidence in support of a new hypothesis of muscular contraction; and, in working through the various German theories, I was dismayed by their lack of clear mechanical conceptions. My next venture was in the physiology of vision, a branch of science which had become almost exclusively German. Starting with a prepossession in favour of one of the dominant German theories, I soon reached the conclusion that the two German leaders in this field, Helmholtz and Hering, with their hosts of disciples, had, in