Page:Popular Science Monthly Volume 50.djvu/467

Rh most elevated kinds have reached those highly integrated, very definite, and extremely heterogeneous organizations they possess, through modifications upon modifications accumulated during an immeasurable past—if the developed nervous systems of such creatures have gained their complex structures and functions little by little; then, necessarily, the involved forms of consciousness which are the correlatives of these complex structures and functions must have arisen by degrees. And as it is impossible truly to comprehend the organization of the body in general, or of the nervous system in particular, without tracing its successive stages of complication; so it must be impossible to comprehend mental organization without similarly tracing its stages."

As in The Principles of Biology the general truths of life were interpreted through the fundamental laws of evolution, so, therefore, in The Principles of Psychology the general facts and problems of mind are elucidated in the same way. The work opens with a consideration of data and inductions, and then—given the psychical shock which Mr. Spencer distinguishes as the primordial and unresolvable element, or ultimate unit, of consciousness—proceeds to trace the evolution of intelligence, stage by stage, through reflex action, instinct, memory, reason, the feelings, and the will. This progress is then exhibited as part of evolution at large; the phenomena belonging to the intellectual, as contradistinguished from the emotional life, are examined in detail; and the ultimate question of the relation between thought and things—between subject and object—is raised and dealt with. Finally, a number of extremely suggestive chapters are devoted to corollaries concerning the expression of feeling, sociality and sympathy, egoistic, ego altruistic, and altruistic sentiments, and the evolution of æsthetic activities and gratifications—all these matters being of great importance in the synthetic system as developing that special part of human psychology upon which sociology and ethics must rely for their foundations.

With the way thus prepared, Mr. Spencer enters upon what, quantitatively considered, represents by far the largest portion of his undertaking—the application of the laws of evolution to the phenomena of society. The Principles of Sociology as actually completed exhibit the only important departure of the author from the prospectus issued thirty-six years ago; for the volume in which linguistic, intellectual, moral, and aesthetic progress was to have been traced out, is left unwritten. Sundry of the more momentous questions connected with these phases of human development, however, are touched upon in other parts of the system, and the hiatus is, therefore, by no means a serious one.