These final months of 1888 were spent in Turin in a state of almost constant euphoria. By December, however, he was exhibiting unmistakable sighs of mental derangement. In a series of crazy letters he expressed the belief he had deposed both the German Emperor and the Pope, had arranged for all anti-Semites to be shot, and that he was, in fact, 'God'. At the beginning of January 1889 he flung his arms around a horse being beaten by a coachman in a Turin piazza, collapsed into tears, and was taken to an asylum, first in Basel then in Jena. Though he did not die until 1900 his final years were spent in a vegetative state. Among doctors who have taken an interest in the question of why, at age 44, Nietzsche went mad, the traditional diagnosis of syphilis is now largely discredited. Though there is speculation that he had a slow-developing brain-tumor, it is more likely he suffered from a bi-polar disorder that eventually developed schizophrenia-like symptoms. ( He saw rifles pointing at him through windows in Jena.)
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).