This book arises from the work carried out within the Seminar "Investigations of the Unconscious", whose main objective is to carry out a systematic review of the complete work of the Swiss psychiatrist and psychologist Carl Gustav Jung.In this sense, the work is based on the reflections made after the revision of volume 10 of Jung's complete works. This is characterized by the cultural and social writings made by the author, in which he particularly addresses the psychic situation of humanity during the years he lived in the twentieth century.We name the "Civilizational Illusion" that belief of humanity in which we assume that we have transcended or overcome our animal instinctive nature from the rational "progress" achieved since the times of the Enlightenment, and even the amazing technological developments that we witnessed during the first twenty years of the twenty-first century.