As regards the criticism encountered by the first edition of this work, I was pleased to find my writings were received with much more open-mindedness among English critics than was the case in Germany, where they are met with the silence born of contempt. I am particularly grateful to Dr. Agnes Savill for an exceptionally understanding criticism in the _Medical Press_. My thanks are also due to Dr. T. W. Mitchell for an exhaustive review in the _Proceedings of the Society for Psychical Research_. This critic takes exception to my heresy respecting causality. He considers that I am entering upon a perilous, because unscientific, course, when I question the sole validity of the causal view-point in psychology. I sympathise with him, but in my opinion the nature of the human mind compels us to take the final point of view. For it cannot be disputed that, psychologically speaking, we are living and working, day by day, according to the principle of directed aim or purpose, as well as that of causality. A psychological theory must necessarily adapt itself to this fact. What is plainly directed towards a goal cannot be given an exclusively causalistic explanation, otherwise we should be led to the conclusion expressed in Moleschott's famous enunciation: "Man _is_, what he eats." We must always bear the fact in mind that _causality is a point of view_. It affirms the inevitable and immutable relation of a series of events: a-b-d-z. Since this relation is fixed, and according to the view-point must necessarily be so, looked at logically the order may also be reversed. _Finality is also a view-point_, that is justified empirically solely by the existence of series of events, wherein the causal connection is indeed evident, _but the meaning of which only becomes intelligible as producing final effect_. Ordinary daily life furnishes the best instances of this. The causal explanation must be mechanistic, if we are not to postulate a metaphysical entity as first cause. For instance, if we adopt Freud's sexual theory and assign primary importance psychologically to the function of the genital glands, the brain is viewed as an appendage of the genital glands. If we approach the Viennese idea of sexuality with all its vague omnipotence, and trace it in a strictly scientific manner down to its psychological basis, we shall arrive at the first cause, according to which psychic life is for the most, or the most important part, tension and relaxation of the genital glands. If we assume for the moment that this mechanistic explanation be "true," it would be the sort of truth which is exceptionally tiresome and rigidly limited in scope. A similar statement would be that the genital glands cannot function without adequate _nourishment_, with its inference that sexuality is an appendage-function of nutrition! The truth contained in this is really an important chapter in the biology of lower forms of life.