This article examines how Nietzsche’s illness bears on his philosophical ideas. It demonstrates that the long-standard explanation for Nietzsche’s dementia—syphilis—is almost certainly false. The cause is much more likely to have been a brain tumor, which had caused him severe headaches and eye problems since childhood. Nietzsche also suffered from a host of digestive problems. It is no wonder that he puts such great weight on “health” and especially the kind of health that overcomes sickness and suffering. When Nietzsche values “madness,” it is a healthy and philosophical madness exemplified in Zarathustra and which Nietzsche tried to cultivate in himself.
This article examines Nietzsche’s moral psychology by focusing on his most important contribution to that form of inquiry, On the Genealogy of Morality. The will to power, understood as a self-standing desire for effective agency, emerges as a central concept. The Genealogy is an exploration of what happens to this desire under circumstances in which its satisfaction is severely restricted. In particular, phenomena playing a role in the development of morality such as ressentiment and self-denial are best understood as expressions of the “will to power of the weak.” And the moral outlook that grows out of them may be understood as a strategy to allow even the “weakest” a “feeling of power.” This moral outlook proves to be a kind of psychopathology insofar as it is an expression of the will to power that undermines the very conditions of its pursuit, satisfaction, and enjoyment—a “will to nothingness.”