It was this powerful and malignant theory which was attacked and answered by the modern idealist school represented by Green, Wallace, and Ritchie, and, in the present day, by Dr. Bosanquet. These writers gave us a theory of the state based on the importance and reality of social purpose. They went back to the theory of the Greek city state expounded by Plato and Aristotle, finding modern reinforcement in the teaching of Rousseau and more especially of Hegel. Their destructive criticism of 'scientific' individualism was reinforced by the teaching of anthropology and of historical jurisprudence, which emphasized the part played in early forms of society by social solidarity and showed the inability of individualism to account for the development of society. Their destructive criticism was, however, the least part of their achievement. They exhibited convincingly the state as the product of will and purpose, based on man's moral nature and being in turn the form in which that moral nature expresses itself. In a notable phrase of Dr. Bosanquet's, a phrase to which he has given constant detailed amplification, 'institutions are ethical ideas'; moral purpose may seem to shine dimly enough in many actual institutions, but it is the only light which shines in them at all, and only in that light can their meaning and reality be understood. The main principles of this idealistic school may be safely said to have by this time established themselves against criticism. Of recent years Social Psychology has done much to explain the gap between the contemplated purpose and the actual working of institutions, and has given precision and definiteness to those elements in human nature which strengthen or weaken social solidarity. Economists have come to see that economic relations are possible only within the framework of a society which has its root in moral and political purpose, although within that framework they may be theoretically isolated and studied by themselves. Sociology, after many false starts, inspired by the mistaken belief that a scientific treatment of society should interpret higher forms in the light of lower, has now found it possible to study the manifold variety of institutional and social life on the basis provided by idealistic philosophy. As a theory of society, in short, this philosophy holds the field. It has been criticized of late years as a theory of the state, and as these criticisms show both where the idealistic theory was in some respects defective and also where the chief problems for political philosophy in the future are to be found, I shall devote the greater part of my lecture to these considerations.