In the scheme of nature Mind is ever associated with Life. The third division of this philosophical system will therefore be Psychology, or the Science of Mind. This great subject will be considered, not by the narrow methods usual with metaphysicians, but in its broadest aspects as a phase of nature's order--to be studied by observation and induction through the whole range of psychical manifestation in animated beings. The subject of mind will be regarded in the light of the great truths of Biology previously established; the connections of mind and life will be traced; the progress of mentality as exhibited in the animal grades, and the evolution of the intellectual faculties in man will be delineated and the cooperation of mind and nature in the production of ideas and intelligence unfolded. We have no work upon mind of this comprehensive and thoroughly scientific character: the materials are abundant, and the necessity of their organization is widely recognized. That Mr. Spencer is eminently the man to perform this great task is proved by the fact that he is already the author of the most profound and able contribution to the advancement of psychological science that has appeared for many years. * * * * * In the true philosophic order, Biology and Psychology prepare the way for the study of social science, and hence the fourth part of Mr. Spencer's system will treat of Sociology, or the natural laws of society. As a knowledge of individuals must precede an understanding of their mutual relations, so an exposition of the laws of life and mind, which constitute the science of human nature, must precede the successful study of social phenomena. In this part will be considered the development of society, or that intellectual and moral progress which depends upon the growth of human ideas and feelings in their necessary order. The evolution of political, ecclesiastical, and industrial organizations will be traced, and a statement made of those principles underlying all social progress, without which there can be no successful regulation of the affairs of society. Mr. Spencer's mind has long been occupied with these important questions, as the reader will find by referring to his able work upon "Social Statics," published several years ago. * * * * *