Husserl founded and developed transcendental phenomenology as an eidetic discipline. It arose, first from its subject matter, but in a decisive way from the scientific and rationalistic (philosophical) goals assigned to it. As to the former, the basic concepts of a science of what is a perpetual flux have to be concepts of types, not fixed or exact concepts as those of the natural sciences, because only they can ­capture the "pronounced conformity to type" of the flux of consciousness.