In the history of Dutch psychiatry an important place is taken by the physician J.N. Ramaer (1817-1887). Ramaer was one of the founders of the Netherlands Association of Psychiatrists and was for some time Inspector for the Insane Asylums. A biography of Ramaer and the history of his famous library was written by Lindeboom (1982). This article is a study of the scientific efforts of Ramaer. It contains a description of the ideas of the German psychiatrist Wilhelm Griesinger who had a strong influence on Ramaer. According to Griesinger psychiatry should be a natural science, in which psychical disturbances were considered as the result of physical causes. In the conception of Griesinger physiology laid the foundation of psychiatry, because this discipline (as opposed to anatomy) made possible the treatment of health and illness as a causal process. Ramaer supported the ideas of Griesinger, especially his stand against the so-called `ontological' thinking, that was considered as the greatest hindrance to a physiological psychiatry. The author concludes, that the program of Ramaer (and Griesinger) was unworkable, because illness and health cannot be conceived in sheer physical terms.