The figure of Justinus Kerner and his most famous work, The Seeress of Prevorst, are often quoted by Carl Gustav Jung. The Swiss analyst became interested in this clinical case of possession during the years of his university studies and in the first years of his profession. Subsequently, when he had already formulated his theory of personalities, he returned to quote The Seeress of Prevorst also extensively, as he did during the seminars of 1933-34 at the Zurich Polytechnic. In Kerner's work Jung saw a forerunner of his work. The purpose of this work is to present Kerner's work by removing it from the field of spiritism in which it is often confined, and to reinsert it in the field of psychological studies; at the same time we will try to highlight how Jung was influenced by this proto-psychoanalytic case.