Vol. I. of "The Principles of Ethics," including Parts I., II., and III., appeared in August, 1892. In this volume, "The Data of Ethics," reprinted as Part I., remains unchanged, except for one or two unimportant sentences. To this Part I. is, however, appended a chapter which was, according to Mr. Spencer, written for the first publication of "The Data of Ethics," but was either put aside for some reason, or else overlooked, probably the latter, says the author, since it contains material which should have been embodied. The chapter is headed "The Conciliation," and seems to correspond to the two chapters on "Trial and Compromise" and "Conciliation" which follow the chapters on "Egoism _versus_ Altruism," and "Altruism _versus_ Egoism"; for it begins with a consideration of the conflict of claims shown by "the last two chapters," the apparent impossibility of the establishment of an equilibrium, and the consequent apparent necessity of self-sacrifice. But this conflict between egoism and altruism is merely transitional and is in process of gradual disappearance, in the same manner in which the present degree of conciliation of the two has been reached,--namely, by the growth of such a constitution in each creature as entails pleasure in altruistic action. Even with the lower animals, the acts which are necessary to care for ova or young are the fulfilment of an instinct which is gratified by the act; and in the human race, conciliation between egoism and altruism, which goes hand in hand with evolution, has reached a high degree. In the evolution of the human race itself, from savagery to its present condition, there has been a marked increase of this conciliation; this is true not only in the family, but to a small extent also with regard to the larger groups of men constituting societies. There is decrease of cruelty, increase of justice, both in the form of state institutions and in their methods of administration, more active benevolence, and a public sentiment that leads large numbers of people to find egoistic gratification in the pursuit of the general good even to the neglect of private interests. Self-sacrifice thus ceases to be sacrifice in the ordinary sense of the word, since it comes to bring with it more pleasure than pain. The future must hold in store changes analogous to those of the past, but these must go on much more rapidly under the present comparatively peaceful organization of society than they have during the militant life of the past. This moral development is retarded, however, not only by the degree of militancy yet existing, but also by the necessity for a certain degree of bluntness of feeling, too great sensitiveness to the suffering of others entailing, while the pressure of population is as great as at present, a misery that would make life intolerable. It is likely that, with social progress, human fertility will decrease as cerebral activity increases,