From The Art and Popular Culture Encyclopedia
A key aspect of Schopenhauer's thought is the investigation of what makes man less than reasonable. This force he calls "Wille zum Leben" or Will (lit. will to life or will to live), by which he means the forces driving man, to remain alive and to reproduce, a drive intertwined with desire. This Will is the inner content and the driving force of the world. For Schopenhauer, Will had ontological primacy over the intellect; in other words, desire is understood to be prior to thought, and, in a parallel sense, Will is said to be prior to being. Schopenhauer's identification of this world-constituting process as an irrational will to live influenced later 19th- and early 20th-century thinking, such as the work of Friedrich Nietzsche and Sigmund Freud.
According to Freud, the Id in the Id, ego, and super-ego is a Freudian psychological concept is responsible for our basic drives such as food, sex, and aggressive impulses. It is amoral and egocentric, ruled by the pleasure–pain principle; it is without a sense of time, completely illogical, primarily sexual, infantile in its emotional development, and will not take "no" for an answer. It is regarded as the reservoir of the libido or "sexual energy".
According to Nietzsche every human action is born of a basic instinct to exercise one's own power in some way. Gift-giving, love, praise, or harmful acts such as physical violence, carrying tales, etc. all stem from the same unconscious motive: to exert the will. The theory of the will to power is not limited to the psychology of human beings. Instead, it is the essential nature of the living universe, manifest in all things. Growth, survival, dominance in business or physical competition, all are seen as elements of this will. See will to power.