Professor Dr. Charles I. McLaren (1882-1957) of the Department of Psychiatry, Severance Union School of Medicine in Seoul, Korea had introduced not only Christianity but medicine and psychiatry of his time with his own theories to Korea while he had served as a Christian missionary from Australia to Korea from 1911 to 1941. Based on his view of Christianity and knowledge of modern science and medicine, he tried to explore the etiology, symptoms, treatment and spiritual meaning of mental disorders including general paresis, dementia praecox, mania, melancholia, paranoia, neurasthnenia, hysteria, hypochondriasis, and even psychophysiological disorder. Though he accepted that mental disorders are related to disrupted functions of brain or neurons, he believed that fundamental causes of insanity is spiritual. Regarding etiology, he suggested that people's choice not to follow God's logos by their free-will and consequent disharmony with nature or human society or failure of self to adapt to reality causes mental disorders. And he explained psychotic phenomena in view of Christian spirituality. In addition, he argued "psychic" (psychological or spiritual) conflict, sensitivity and guilt feeling as a possible etiology of psycho-neurosis including neurasthenia, hysteria and hypochondria. Conflict includes not only sexual conflicts but social conflicts related to family, job, money, or guilt feeling. He also emphasized the meaning and purpose of life in relation to development of mental illness. Remarkably, he introduced idea of "spill-over" to explain how emotional problems influence autonomic dysfunction resulting in psycho- physiological symptoms. He can be recognized as a psychiatrist who integrated bio-medical descriptive psychiatry with psycho-social approach, dynamic psychotherapy and even spiritual approach as a fundamental one. Though many scientific criticism can be given to his theories of psychaitry, he is deserved to be rediscovered and recognized as a pioneer who had shown another apprach to mental disorders to present psychiatrists who are lost in confusion with so many uncertainties in regard to understanding and treating mental disorders.