Freud acknowledged that his use of the term "Id" ("das Es", "the It") derives from the writings of Georg Groddeck. The super-ego is the moral component of the psyche. The rational ego attempts to exact a balance between the impractical hedonism of the id and the equally impractical moralism of the super-ego; it is the part of the psyche that is usually reflected most directly in a person's actions. When overburdened or threatened by its tasks, it may employ defence mechanisms including denial, repression, undoing, rationalization, and displacement. This concept is usually represented by the "Iceberg Model". This model represents the roles the id, ego, and super- ego play in relation to conscious and unconscious thought.