Freud makes a general metapsychological introduction to the psyche and at the same time he undertakes a metapsychological investigation about dreams in the seventh chapter of The interpretation of dreams. In the psychic system he describes, during sleep the intrapsychic direction of the stimuli is reversed, whereas during the wakeful state they proceed from the sensory end to the conscious-motor end. During sleep inner stimuli regress to the sensory end in the regressive motion and constitute dreams, which are experienced on a sensory level. Freud explains how dreams occur in this way and besides investigates the mechanisms that cause this regressive movement and so sheds light on the origin of dreams. But he notifies that dreams also have an incomprehensible center. This article is an essay to step to the incomprehensible center of the dreams, in the light of Freud's last thesis.