In 1923, Freud introduced a model of the "psychic apparatus" in "The Ego and the Id", the "structural model", which could appropriately account for a dynamic view of the mind and mental life. In the following decade, Freud further elaborated the structural model and "The Dissection of the Psychical Personality", his XXXI. Lecture of the "New Introductory Lectures on Psycho-Analysis", spelled out the result of this specification. The present new edition of these two texts is newly commented and provided with a systematic introduction, which presents Freud's theory of the mind from the point of view of contemporary psychoanalytic research and brings it into an interdisciplinary dialogue with current approaches in cognitive research.