Jaspers Psychopathology (1913) encompasses all areas of psychiatry and delves deeply into psychology and philosophy. From the beginning it has had a great repercussion in European, Japanese, Latin American and finally, in the English speaking psychiatry. Jaspers greatest achievement was to establish psychopathology as a hard science and the basis of psychiatry as professional practice. He did this from strictly methodological perspective. Besides, he aspired to consider the patient and his psychopathological manifestations on the horizon of the totality of existence. To summarize his contributions would be practically impossible. Therefore, these authors have focused this chapter on some particular topics of his work, such as the introduction of phenomenological method; the development of the method of understanding in contrast to explanation; the concepts of process and development; the overcoming of stimulus/response scheme for conceptualizing the man-world relationship and its replacement by his revolutionary concept of “situation”; and finally, the introduction of dialectical thinking in psychopathology and psychiatry.