 From these two main classes, Stumpf distinguished within his classification three neutral sciences whose task is to study the structure of the contents of psychical functions and sense phenomena in general. Stumpf claims that they represent three different fields of research, corresponding to three distinct sciences: phenomenology as the science of phenomena, eidology which studies formations, and the general theory of relations understood as the science of relations as a whole. These three new sciences are said to be “neutral” with regard to existing sciences and they are “propaedeutic sciences” in that their field of study represents the raw material and the starting point of the natural sciences as well as the social sciences. To use Stumpf’s terms, they are the atrium and the organon of all sciences and of philosophy.