Criticizing the tendency to treat Nietzsche as a literary figure or as a vitalist in the tradition of Bergson, Simmel, and Klages, Lowith situates Nietzsche squarely within the history of Western philosophy. He takes issue with the position of Jaspers that Nietzsche is best read as a rejection of all philosophical certainties and challenges Heidegger's view that Nietzsche was the last metaphysician of the West.

For Lowith, the centerpiece of Nietzsche's thought is the doctrine of eternal recurrence, a notion which Lowith, unlike Heidegger, deems incompatible with the will to power.

His careful examination of Nietzsche's cosmological theory of the infinite repetition of a finite number of states of the world suggests the paradoxical consequences this theory implies for human freedom. How is it possible to will the eternal recurrence of each moment of one's life, if both this decision and the states of affairs governed by it appear to be predestined?

Lowith's book, one of the most important, if seldom acknowledged, sources for recent Anglophone Nietzsche studies, remains a central text for all concerned with understanding the philosopher's work.