General literature, even in its highest forms, seems to reflect a corresponding change of view as to what is of most worth in life. Already the strong hold on duty and the spiritual world which Tennyson unfalteringly displayed, even the deeper insight into motive and the faith in goodness which are shown by Browning, are read by us as utterances of a past age. We have grown used to a presentment of human life such as Ibsen's in which the customary morality is regarded as a thin veneer of convention which hardly covers the selfishness in grain, or to the description of life as a tangled mass of animal passions,--a description which, in spite of the genius of Zola, does not fail to weary and disgust,--or perhaps as only a spectacle in which what men call good and evil are the light and shade of a picture which may serve to produce some artistic emotion. An attitude akin to these becomes an ethical point of view in Nietzsche, the _enfant terrible_ of modern thought, who maintains that man's life must be interpreted physiologically only and not spiritually, and who would replace philanthropy by a boundless egoism. Influences of the second kind are usually more prominent than the preceding in the case of the philosophical moralist, and they are not always avoided by the moralist who boasts his independence of philosophy. The former influences are more constantly at work: they supply the facts for all ethical reflexion. Ethical thought is not so uniformly influenced by the conceptions arrived at in science or philosophy. But there are certain periods of history in which conceptions regarding the truth of things--whether arrived at by scientific methods or not--have had a profound influence upon men's views of good and evil. At the beginning of our era, for instance, the view of God and man introduced by Christianity, resulted in a deepened and, to some extent, in a distinctive morality. Again, at the time of the Renaissance, the new knowledge and new interests combined with the weakening of the Church's and of the Empire's authority to bring about the demand for a revision of the ecclesiastical morality, and led to some not very successful attempts to find a firmer basis for conduct. At the present day also it is the case that philosophers of different schools are for the most part agreed in claiming ethical importance for their conceptions about reality. In particular, the scientific thought of the last generation has been reformed under the, influence of the group of ideas which constitute the theory of evolution. There is hardly a department of thought which this new doctrine has not touched; and upon morality its influence may seem to be peculiarly important and direct. The theory of evolution, as put forward by Darwin, has established certain positions which have been regarded as of special significance for ethics.