The nucleus of this little book is formed by an article on 'Ethics' which I wrote some years ago for the Encyclopedia Britannica. I found that, in the opinion of persons whose judgment had weight with me, this article appeared likely to meet the needs of English students desirous of obtaining a general knowledge of the history of ethical thought; I have, therefore, by the permission of Messrs. Black, the publisher of the Encyclopedia Britannica, reprinted it in this separate from. In so doing, I have considerably altered and enlarged it; but, after some hesitation, I determined to adhere to the main outlines of the original article, according to which the chapter (IV).