were under constant threat of removal to a concentration camp until 30 March 1945, when Heidelberg was occupied by American troops. In 1948 Jaspers moved to the University of Basel in Switzerland. In 1963 he was awarded the honorary citizenship of the city of Oldenburg in recognition of his outstanding scientific achievements and services to occidental culture. He remained prominent in the philosophical community and became a naturalized citizen of Switzerland living in Basel until his death on his wife's 90th birthday in 1969. Contributions to psychiatry Jaspers's dissatisfaction with the popular understanding of mental illness led him to question both the diagnostic criteria and the methods of clinical psychiatry. He published a paper in 1910 in which he addressed the problem of whether paranoia was an aspect of personality or the result of biological changes. Although it did not broach new ideas, this article introduced a rather unusual method of study, at least according to the norms then prevalent. Not unlike Freud, Jaspers studied patients in detail, giving biographical information about the patients as well as notes on how the patients themselves felt about their symptoms. This has become known as the biographical method and now forms a mainstay of psychiatric and above all psychotherapeutic practice. Jaspers set down his views on mental illness in a book which he published in 1913, General Psychopathology. This work has become a classic in the psychiatric literature and many modern diagnostic criteria stem from ideas found within it. One of Jaspers's central tenets was that psychiatrists should diagnose symptoms of mental illness (particularly of psychosis) by their form rather than by their content. For example, in diagnosing a hallucination, it is more important to note that a person experiences visual phenomena when no sensory stimuli account for them, than to note what the patient sees. What the patient sees is the "content", but the discrepancy between visual perception and objective reality is the "form". Jaspers thought that psychiatrists could diagnose delusions in the same way. He argued that clinicians should not consider a belief delusional based on the content of the belief, but only based on the way in which a patient holds such a belief. (See delusion for further discussion.) Jaspers also distinguished between primary and secondary delusions. He defined primary delusions as autochthonous, meaning that they arise without apparent cause, appearing incomprehensible in terms of a normal mental process. (This