In Chapter XXI (Sec 86), I have spoken of the hesitating utterances of moralists touching any duties we may owe to the brutes. I suggest that before anyone dogmatize in detail on this subject he read with some care such a comprehensive work as Miss Washburn's _The Animal Mind_. The book is admirable. Chapters x and xliv of Westermarck's work are instructive and entertaining on this subject. Hegel disposes of the animals rather summarily. See his _Philosophy of Right_, Sec 47. Sidgwick, _The Methods of Ethics_, Book III, chapter iv, 2, is well worth consulting. See in my own volume, Chapter XXX, Sec 141. For Chapter XXII, I give no references. I appeal only to the common sense of my reader. 7. Chapters XXIII to XXIX.--For the chapters on the Schools of the Moralists, XXIII to XXIX, I shall give briefer notes than I should have given, were the chapters not already so well provided with foot-notes. So far as the first four of these chapters are concerned, I shall assume that enough has been said, drawing attention only to two points which concern Chapter XXIII. It is very interesting to note that one of our best critics of intuitionism, Hemy Sidgwick, was himself an intuitionist. His _Methods of Ethics_ deserves very close attention. Again Intuitions are often spoken of as if they had been shot out of a pistol, and had neither father nor mother. To understand them better it is only necessary to read chapter viii of Dr. H. R. Marshall's little book, _Mind and Conduct_, which shows how difficult it is to mark intuitions off sharply, and to treat them as if they had nothing in common with reason. Those interested in the ethics of evolution, treated in Chapter XXVII, should not miss reading the fourth chapter of Darwin's _Descent of Man_. Huxley's essay, _Evolution and Ethics_, might be read. The "Prolegomena" to the essay is, however, much more valuable than the essay itself. Spencer's general theory of conduct is best gathered from his _Data of Ethics_, which was reprinted as Part I of his _Principles of Ethics_. The volume by C. M. Williams, entitled, _A Review of Evolutionary Ethics_, gives a convenient account of a dozen or more writers who have treated of ethics from the evolutionary standpoint. It is well not to overlook what Sidgwick has to say of evolution and ethics; see _The Methods of Ethics_, Book I, chapter ii, Sec 2. As for Chapter XXVIII, on "Pessimism," it is enough, I think, to refer the reader to Book IV, in Schopenhauer's work on _The World as Will and Idea_. The Book is entitled _The Assertion and Denial of the Will to Live, where Self-consciousness has been Attained_. See also his supplementary chapters, xlvi, on "The Vanity and Suffering of Life," and xlviii, "On the Doctrine of the Denial of the Will to Live." For the doctrine of von Hartmann, see chapters xiii to xv, in the part of his work entitled, _The Metaphysic of the Unconscious_.