Whoever denies overindividual reality finds himself in the world of phenomena a solipsist and in the world of purposes a sceptic:  there is no objective physical world, everything is my idea, and there is no objective value, no truth, no morality, everything is my individual decision.  But to deny truth and morality means to contradict the very denial, because the denial itself as judgment demands acknowledgment of this objective truth and as action demands acknowledgment of the moral duty to speak the truth.  And if an overindividual purpose cannot be denied, it follows that there is a community of individual subjects whose phenomena cannot be absolutely different:  there must be an objective world of overindividual objects.

In each of the four groups of sciences we must consider the facts either with regard to the general relations or with regard to the special material; the abstract general relations refer to every possible material, the concrete facts which fall under them demand sciences of their own.  In the world of phenomena the general relations are causal laws—­physical or psychical laws; in the world of purposes theories of teleological interrelations—­normative or historical; the specific concrete facts are in the world of phenomena objects, physical or psychical objects, in the world of purposes acts of will—­specific norms or historical acts.  If we turn first to phenomena, the laws thereof are expressed in the physical sciences, by mechanics, physics, chemistry, and we make mechanics the superior as chemistry must become ultimately the mechanics of atoms.  In the psychological sciences the science of laws is psychology, with the side-branch of animal psychology, while human psychology refers to individuals and to social groups.  Social psychology, as over against individual psychology, is thus a science of general laws, the laws of those psychological phenomena which result from the mutual influence of several individuals.

On the other hand, we have as the special concrete products of the laws, the objects themselves, and the most natural grouping of them may be from whole to part.  In the physical world it means that we start from the concrete universe, turning then to the earth, then to the objects on the earth, inorganic and organic.  There is here no logical difficulty.  Each one of these objects can be considered in three aspects, firstly as to its structure, secondly as to its special laws, that is, the special function of the object as related to the general sciences of physics and chemistry, and thirdly as to its natural development.  If we apply these three methods of study to the whole universe we have astronomy, astrophysics and cosmology, to the whole earth, geography, geophysics, geology, to animals, zooelogy, physiology, comparative anatomy, and so on.