Schizophrenia, delusions, and Heidegger's "ontological difference"
By definition, all psychoses involve disturbed judgement and acceptance of some kind of altered reality. Only in schizophrenia, however, do we find delusions and hallucinations that can be described—in Karl Jaspers's words—as "mad in the literal sense," that is, as concerning situations that are not only false but virtually inconceivable or incomprehensible because they imply alterations in the most fundamental structures of time, space, causality, or human identity. Thus schizophrenic delusions will often involve cosmic or nihilistic fantasies that can only be described as bizarre: the patient may claim, for instance, that everyone else in the world is but an automaton devoid of human consciousness; that the entire universe is on the verge of dissolution; that all the clocks in the world feel the patient's pulse; or that when his eyes get bright blue, the sky also turns blue (Jaspers 1963, pp 577, 296).1 By contrast, in the other "functional" psychoses (manic-depressive illness and pure paranoia), the prominent symptoms tend to involve beliefs or experiences that could occur in real life or that can at least be comprehended as exaggerations of normal fears and fantasies—as, for example, when patients have thoughts of being followed or poisoned or admired by multitudes (American Psychiatric Association 1987, p 202).
Sass, L. (1992)., Schizophrenia, delusions, and Heidegger's "ontological difference", in M. Spitzer, M. A. Schwartz & M. A. Schwartz (eds.), Phenomenology, language & schizophrenia, Dordrecht, Springer, pp. 126-143.
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