The Four Domains of Mental Illness presents an authentic and valid alternative to the DSM-5, which author René J. Muller argues has resulted in many patients being incorrectly diagnosed and wrongly medicated. Dr. Muller points out where the DSM-5 is mistaken and offers a guide to diagnosis based on the psychobiology of psychiatrist Adolf Meyer and the insights of existential philosophy and psychiatry. His model identifies the phenomena of the mental illnesses that clinicians most often see, which are characterized by identifying their structure, or partial structure. Using the FDMI approach, clinicians can grasp how each mental illness is an aberration of Martin Heidegger’s being-in-the-world.