Classical philologist turned iconoclast, Nietzsche is the hinge between 19th-century philosophy and almost everything that came after in continental thought. He is also the most widely misread major philosopher — by turns claimed by existentialists, postmodernists, literary critics, Nazis (who falsified him), and anti-Nazis. Read him in his own books and a coherent project emerges: a sustained attempt to diagnose the cultural condition of Europe after the collapse of Christian metaphysics and the moral framework built on it.
"God is dead," he announced in The Gay Science (1882) — not a triumphant atheist slogan but a worried diagnosis. The sustaining religious worldview had lost its grip on educated Europeans, but the moral values it underwrote (humility, equality, concern for suffering) kept shambling on without their foundation. Nietzsche feared this would yield nihilism and the "last man" — a comfortable, uncurious creature who has made happiness into his only project.
His genealogical method — most fully developed in On the Genealogy of Morals (1887) — asks not whether moral values are true but where they came from and what kind of life produced them. The answer he gave was provocative: Christian-modern morality is a "slave morality," born of resentment against aristocratic flourishing, which inverted noble values by making weakness into virtue. Whatever one makes of the thesis, the method — reading values as artifacts of specific historical power-configurations — had enormous downstream impact, visible in Michel Foucault, in critical theory, and in contemporary debates about the origins of our moral vocabulary.