How did Karl Jaspers use phenomenology in the study of mental illness?

Karl Jaspers applied phenomenology to clinical psychiatry by focusing on the direct investigation and description of a patient's conscious experiences.1

At the time, Jaspers observed that psychiatry lacked a systematic framework and relied heavily on diagnosis without adequate descriptive methods. To address this, he utilized phenomenology to describe symptoms as they were experienced by the individual, intentionally setting aside theories regarding their causal or biological explanations. This approach allowed for a more precise language to describe mental states, facilitating the recognition of similar symptoms across different cases.1

His work in this area culminated in his influential textbook, General Psychopathology, which was distinguished by its critical evaluation of various psychiatric methods and its attempt to synthesize them into a cohesive scientific framework. By prioritizing the patient's subjective experience, Jaspers helped establish psychopathology as a rigorous scientific discipline.1