Considered by many as one of his most important works, "The Genealogy of Morals" is a collection of three essays on Nietzsche's "thoughts on the origin of our moral prejudices". In the three essays ("'Good and Evil,' 'Good and Bad'"; " "'Guilt', 'Bad Conscience', and the like'"; and "What is the meaning of ascetic ideals?") Nietzsche reflects upon the genealogical hypothesis of morality put forth in his friend Paul Rée's work "The Origin of the Moral Sensations". Finding this theory unsatisfactory Nietzsche calls for an examination of moral values themselves, writing "the value of these values themselves must be called into question."