SOURCE: Sass, Louis A. “On Delusions.” Raritan: Quarterly Review 9 (spring 1990): 120-41.

In the following essay, Sass discusses Schreber's Memoirs in the context of traditional interpretations of schizophrenic delusions.

You must always be puzzled by mental illness. The thing I would dread most, if I became mentally ill, would be your adopting a common-sense attitude; that you could take it for granted that I was deluded.

—Ludwig Wittgenstein

Insanity is generally assumed to involve perceiving things that do not exist and believing things that are not true. As Karl Jaspers (an influential psychiatrist before he became a philosopher) put it, “Since time immemorial, delusion has been taken as the basic characteristic of madness. To be mad was to be deluded.” This remains true in contemporary psychiatry and clinical psychology, at least in America, where “disturbance in or failure of reality testing” is considered to be the criterion for the...