Our research will go this way: from the center of artistic and philosophical problems to the periphery. We will begin with basic concepts and end with some private and topical issues, on which only in this way full light can be shed. But in the interest of fundamental knowledge, it seemed to me that a detailed development of the topic was necessary. Each general concept is distinguished by the special nature of its branches; and only a glance cast at the mode of individuation completes the knowledge of the basic principle. However, it is neither possible nor necessary to trace all individual branches; a few characteristic examples are sufficient for us: and I choose those that interest us especially closely today.