The philosophers, who have learned that correct and highly complicated thought structures are possible even without the cooeperation of consciousness, have found it difficult to attribute any function to consciousness; it has appeared to them a superfluous mirroring of the perfected psychic process. The analogy of our Cons. system with the systems of perception relieves us of this embarrassment. We see that perception through our sensory organs results in directing the occupation of attention to those paths on which the incoming sensory excitement is diffused; the qualitative excitement of the P-system serves the mobile quantity of the psychic apparatus as a regulator for its discharge. We may claim the same function for the overlying sensory organ of the Cons. system. By assuming new qualities, it furnishes a new contribution toward the guidance and suitable distribution of the mobile occupation quantities. By means of the perceptions of pleasure and pain, it influences the course of the occupations within the psychic apparatus, which normally operates unconsciously and through the displacement of quantities. It is probable that the principle of pain first regulates the displacements of occupation automatically, but it is quite possible that the consciousness of these qualities adds a second and more subtle regulation which may even oppose the first and perfect the working capacity of the apparatus by placing it in a position contrary to its original design for occupying and developing even that which is connected with the liberation of pain. We learn from neuropsychology that an important part in the functional activity of the apparatus is attributed to such regulations through the qualitative excitation of the sensory organs. The automatic control of the primary principle of pain and the restriction of mental capacity connected with it are broken by the sensible regulations, which in their turn are again automatisms. We learn that the repression which, though originally expedient, terminates nevertheless in a harmful rejection of inhibition and of psychic domination, is so much more easily accomplished with reminiscences than with perceptions, because in the former there is no increase in occupation through the excitement of the psychic sensory organs. When an idea to be rejected has once failed to become conscious because it has succumbed to repression, it can be repressed on other occasions only because it has been withdrawn from conscious perception on other grounds. These are hints employed by therapy in order to bring about a retrogression of accomplished repressions.