This book offers a phenomenologically informed reading of some fundamental positions of the philosophical tradition. Its objective is not that of giving an exhaustive account of the thinking of any single philosopher, much less of the trajectory of philosophy as a whole; rather, the aim is to retrace a few key moments in the course of philosophical enquiry, from its outset to its accomplishment in Nietzsche's metaphysics, with a focus on the main motive of that enquiry: the always new attempt to establish a sufficient knowledge of the ultimate principle on which to build a human "ethos".