The phenomena which are comprised under the title of the “life of the soul,” or the psychic activity, are, on the one hand, the most important and interesting, on the other the most intricate and problematical, of all the phenomena we are acquainted with. As the knowledge of nature, the object of the present philosophic study, is itself a part of the life of the soul, and as anthropology, and even cosmology, presuppose a correct knowledge of the “psyche,” we may regard psychology, the scientific study of the soul, both as the foundation and the postulate of all other sciences. From another point of view it is itself a part of philosophy, or physiology, or anthropology.

The great difficulty of establishing it on a naturalistic basis arises from the fact that psychology, in turn, presupposes a correct acquaintance with the human organism, especially the brain, the chief organ of psychic activity. The great majority of “psychologists” have little or no acquaintance with these anatomical foundations of the soul, and thus it happens that in no other science do we find such contradictions and untenable notions as to its proper meaning and its essential object as are current in psychology.