Many psychologists and philosophers have denied the existence of special laws for our psychical life, if we understand this to mean specific laws, differing from the universal physical ones. Some say that everything that is called a psychical law is nothing but a psychological reflex of physical combinations, which is made up of sensations joined to certain central cerebral processes. Others maintain that there are no laws at all in the mental sphere. They say that the essential difference between natural and mental sciences consists in the fact that only the former can be reduced to definite laws, whereas the latter are absolutely wanting in any arrangement of phenomena according to law. The first of these opinions, that of materialistic psychology, can be passed over rapidly. It is contradicted by all the phenomena of consciousness that we have up till now discussed. It is contradicted by the fact of consciousness itself, which cannot possibly be derived from any physical qualities of material molecules or atoms. The indisputable affirmation, that there exist no processes of consciousness that are not in some manner or other connected with physical processes, is changed by this materialistic hypothesis into the dogma that the processes of consciousness themselves are in their real essence physical processes. Now this is an assertion that directly contradicts our immediate experience, which teaches us that a human being, or any other similar living creature, is a psycho-physical and not only a physical unity.