Abstract
This paper is devoted to a comparison between Ernst Mach's and Friedrich Nietzsche's anti-metaphysical approach to scientific and philosophical concepts. By making reference to Mach’s early essay on the conservation of energy (Die Geschichte und die Wurzel des Satzes von der Erhaltung der Arbeit, 1872), I argue that Nietzsche shares with him the idea that the concepts we adopt are only useful fictions developed during the history of humankind and its culture. This idea is fundamental for the development of modern science, since Mach’s epistemology contributed to give up the mechanistic (Newtonian) view of physics.