In Nietzsche's philosophy we can locate four major demarcations for the concept of will. (1) There is the appearance of the primal will in the youthful work of the birth of tragedy. This is the metaphysical will of Schopenhauer and it is related to the playful building and destroying of life itself, designated by the principle of becoming and mirrored by the art form of music. (2) There is, to jump ahead into the Nachlass, the theory of will to power which involves a quasi-mechanistic analysis of becoming (viz., the will as force). (3) There is, again in the Nachlass, a notion of will to power which sees in the concept of will a certain power to interpret (this is the will as valuation). (4) There is finally, in the childlike Zarathustra, a concept of the will that involves a kind of saying. It is, specifically, the Ja-and Nein-Sagen of the Uber-and Untermensch. Now the question to ask is the following: Can these manifold uses of the term "will" be unified? An affirmative answer will form an image of Nietzsche's philosophy as a whole. To anticipate: The theory (#2) is an interpretation (#3) of becoming (#1) which requires, on the part of the individual, a yes-saying (#4).
The appearance of the 'Will' in The Birth of Tragedy
The "Will" in Thus Spoke Zarathustra
The "theory" of Will to Power (Nachlass)
The "notion" of Will to Power (Nachlass)
Summary: The Unity of Will to Power