In this third edition I have again made extensive alterations, and introduced a considerable amount of new matter. Some of these changes and additions are due to modifications of my own ethical or psychological views; but I do not think that any of these are of great importance in relation to the main subject of the treatise. And by far the largest part of the new matter introduced has been written either (1) to remove obscurities, ambiguities, and minor inconsistencies in the exposition of my views which the criticisms[5] of others or my own reflection have enabled me to discover; or (2) to treat as fully as seemed desirable certain parts or aspects of the subject which I had either passed over altogether or discussed too slightly in my previous editions, and on which it now appears to me important to explain my opinions, either for the greater completeness of my treatise,--according to my own view of the subject,--or for its better adaptation to the present state of ethical thought in England. The most important changes of the first kind have been made in chaps. i. and ix. of Book i., chaps, i.-iii. of Book ii., and chaps. i., xiii., and xiv. of Book iii.: under the second head I may mention the discussions of the relation of intellect to moral action in Book i. chap. iii., of volition in Book i. chap. v., of the causes of pleasure and pain in Book ii. chap. vi., of the notion of virtue in the morality of Common Sense in Book iii. chap. ii., and of evolutional ethics in Book iv. chap. iv. (chiefly). I may add that all the important alterations and additions have been published in a separate form, for the use of purchasers of my second edition. FOOTNOTE: [5] I must here acknowledge the advantage that I have received from the remarks and questions of my pupils, and from criticisms privately communicated to me by others; among these latter I ought especially to mention an instructive examination of my fundamental doctrines by the Rev. Hastings Rashdall. PREFACE TO THE FOURTH EDITION