Ce troisième volume de la correspondance de Nietzsche couvre la période qui va de janvier 1875 à décembre 1879 : cinq années décisives, intenses et douloureuses dans la vie de Nietzsche, marquées par la maladie, la découverte de l'Italie, la rupture avec Wagner et la publication, sous le patronage surprenant de Voltaire, des aphorismes libérateurs et lucides d'Humain, trop humain. Pareille évolution aurait-elle été possible, cependant, sans la présence de plus en plus marquée dans la vie de Nietzsche d'une maladie aux causes obscures, mais sans cesse plus cruelle - décembre 1875 marquant un moment particulièrement terrible - et qui oblige Nietzsche à renoncer progressivement à son enseignement de la littérature grecque à Bâle et à chercher sans relâche le climat le moins défavorable à sa santé, dans une quête qui le conduira notamment dans l'Oberland et l'Engadine. Enrichie par des extraits des lettres de ses correspondants, la correspondance de Nietzsche, arrachée le plus souvent à des moments de terrible souffrance, brille pourtant de tout son talent de styliste ; plus que jamais, même quand elle fait entendre une longue plainte, sa voix est portée par une étrange énergie, l'expression d'une confiance : la conviction d'être un penseur d'exception. Celui du "gai savoir" à venir.
Friedrich Wilhelm Nietzsche was a German classical scholar, philosopher, and critic of culture, who became one of the most influential of all modern thinkers. He began his career as a classical philologist before turning to philosophy. He became the youngest person to hold the Chair of Classical Philology at the University of Basel in 1869 at the age of 24, but resigned in 1879 due to health problems that plagued him most of his life; he completed much of his core writing in the following decade. In 1889, at age 44, he suffered a collapse and afterward a complete loss of his mental faculties, with paralysis and probably vascular dementia. He lived his remaining years in the care of his mother until her death in 1897 and then with his sister Elisabeth Förster-Nietzsche. Nietzsche died in 1900, after experiencing pneumonia and multiple strokes. Nietzsche's work spans philosophical polemics, poetry, cultural criticism, and fiction while displaying a fondness for aphorism and irony. Prominent elements of his philosophy include his radical critique of truth in favour of perspectivism; a genealogical critique of religion and Christian morality and a related theory of master–slave morality; the aesthetic affirmation of life in response to both the "death of God" and the profound crisis of nihilism; the notion of Apollonian and Dionysian forces; and a characterisation of the human subject as the expression of competing wills, collectively understood as the will to power. He also developed influential concepts such as the Übermensch and his doctrine of eternal return. In his later work, he became increasingly preoccupied with the creative powers of the individual to overcome cultural and moral mores in pursuit of new values and aesthetic health. His body of work touched a wide range of topics, including art, philology, history, music, religion, tragedy, culture, and science, and drew inspiration from Greek tragedy as well as figures such as Zoroaster, Arthur Schopenhauer, Ralph Waldo Emerson, Richard Wagner, Fyodor Dostoevsky, and Johann Wolfgang von Goethe. After his death, Nietzsche's sister Elisabeth became the curator and editor of his manuscripts. She edited his unpublished writings to fit her German ultranationalist ideology, often contradicting or obfuscating Nietzsche's stated opinions, which were explicitly opposed to antisemitism and nationalism. Through her published editions, Nietzsche's work became associated with fascism and Nazism. 20th-century scholars such as Walter Kaufmann, R.J. Hollingdale, and Georges Bataille defended Nietzsche against this interpretation, and corrected editions of his writings were soon made available. Nietzsche's thought enjoyed renewed popularity in the 1960s and his ideas have since had a profound impact on 20th- and early 21st-century thinkers across philosophy—especially in schools of continental philosophy such as existentialism, postmodernism, and post-structuralism—as well as art, literature, music, poetry, politics, and popular culture.