Kurt Schneider's principal work Clinical Psychopathology is generally considered to be a comprehensive textbook of psychopathology similar to General Psychopathology by Karl Jaspers. However, Schneider's book focuses exclusively on the diagnosis and classification of mental disorders, and his methods are based on the assumption that only some mental disorders are diseases. He defines disease in the context of psychiatry and introduces the key concept of break in continuity of meaning of life development. He divides mental disorders into three major groups: abnormal variations of psychic life, somatic process-based psychosis (organic, symptomatic, and toxic psychoses), and somatic process-postulated psychosis (endogenous psychosis). There are four different types of psychiatric diagnoses, in decreasing degree of severity: differential diagnosis in somatic process-based psychosis, differential "diagnosis" that assesses whether a disorder is psychosis, differential typologies in endogenous psychoses, and pure typologies in abnormal variations of psychic life. Schneider always keeps his eyes on the scientific aspect of psychiatry and strives to establish a practical clinical psychiatry, an approach that informs the essence of his book. Here, we examine the application of his views to current psychiatric thinking, as follows:
 ▶By recognizing critical differences between psychiatry and medical science, we can explain to patients the characteristics of their psychiatric diagnosis and classification.
 ▶When a mental disorder is assigned to one of the three groups described above, we can recognize the direction the research should proceed in and what we should pay attention to.
 ▶If a new disorder is proposed, we can refer to Schneider's work to confirm which of the three mental disorder groups it belongs to and discuss appropriate treatment and management.
 ▶We must gain perspective into the patient's life to examine the continuity of meaning of life development. In doing so, they can recover from low self-esteem. Providing such care on a daily basis can have a therapeutic effect on patients.
 ▶Mental competency should be evaluated in individuals charged with a crime who are suspected to have a mental disorder at the time of the crime. If the individual is diagnosed with a mental disorder, lawyers should emphasize the importance of confirming whether the mental disorder is a disease or not.
 <Author's abstract>