In the Preface, Nietzsche describes his journey to writing On the Genealogy of Morals and his investigation of the concepts of good and evil, as well as the values humans assign to these categories. From an early age, Nietzsche was instinctively skeptical. He was interested in morality and its origins and challenged the accepted views of a virtuous life. He recalls struggling at the age of 13 with the concept of evil. At the time, he decided to attribute to God all evil. When he was older, he recognized that pointing to the supernatural as the source of evil was indicative of an a priori approach—philosophical assumptions based upon preconceived ideas and concepts. As he grew older, Nietzsche distinguished between the theological principles he was taught from a young age and what he refers to as “moral prejudice.”

Nietzsche emphasizes the importance of being familiar with his earlier work to understand the concepts he presents in On the Genealogy of Morals. The philosopher was first inspired to publish his own ideas about morality after reading Dr. Paul Rée’s 1877 work The Origin of Moral Sentiments. Nietzsche both admired and vehemently disagreed with Rée’s arguments, so he published Human, All Too Human as a reaction.