What is psychology? This is the question the book attempts to answer from many different perspectives, but the central problem is the one that primarily interested Nietzsche: the problem of self-knowledge and the relationship between that problem and knowledge of the actions and words of others. It would be fair to say, at least, that Nietzsche's most prominent characterization of the theses of self-knowledge and knowledge of others lies in maintaining that it is extremely difficult to achieve this, partly because it is neither empirical nor a priori knowledge, but more so because in his considerations it is always an expression of some self-deception that must be overcome. In this way, Pippin offers a book that allows us to analyze these questions and opens the way for a more precise reading of Nietzsche's philosophy.