It is in this section that Nietzsche discusses at length the points of divergence between his life principle and that of Darwin. And it is here also that he treats of the psychology of pleasure and pain in their relation to the will to power. This latter statement is of great importance in an understanding of the instincts of life as he taught them, for it denies both pleasure and pain a place in the determining of acts. They are both, according to him, but accompanying factors, never causes, and are but second-rate valuations derived from a dominating value. He denies that man struggles for happiness. To the contrary, he holds that all expansion and growth and resistance--in short, all movement--is related to states of pain, and that, although the modern man is master of the forces of nature and of himself, he is no happier than the primeval man. Why, then, does man struggle for knowledge and growth, knowing that it does not bring happiness? Not for existence, because existence is already assured him. But for power, for the feeling of increased mastery. Thus Nietzsche answers the two common explanations of man's will to action--the need for being and the desire for happiness--by his doctrine of the will to power. The entire teaching of Nietzsche in regard to classes and to the necessity of divergent moral codes to meet the needs of higher and lower castes, is contained in the third part of the first book. Here again he emphasises the need of two codes and makes clear his stand in relation to the superior individual. As I have pointed out in preceding chapters, Nietzsche did not attempt to do away with the morality of the inferior classes. He saw that some such religious belief as Christianity was imperative for them. His fight was against its application to all classes, against its dominance. I mention this point again because it is the basis of the greatest misunderstanding of Nietzsche's philosophy. Part III is written for the higher man, and if this viewpoint is assumed on the part of the reader, there will be no confusion as to doctrines encountered. The statements in this section are in effect similar to those to be found in Nietzsche's previous works, but in every instance in the present case they are directly related to the will to power. Because of this they possess a significance which does not attach to them in antecedent volumes.